When it comes to gauging public opinion, the importance of social media is generally overstated. Online conversations frequently happen in an echo chamber populated by likeminded people. This is especially true of Twitter politics. Yet it was social media that hinted to me, early last summer, that longshot lefty Jeremy Corbyn might just end up as leader of the Labour party. “I think he’s going to do it,” I kept telling people as they laughed in my face. “Seriously.”

I say this not so I can go “I told you so”, but as a way of illustrating how, even from the beginning, the spirit of optimism that seemed to propel Corbyn’s campaign was being disbelieved and dismissed in some quarters. This was especially true as said optimism was largely coming from young people who, with their smartphones and their selfies and their 24/7 lifestreams, are so easily derided as superficial and unworldly.

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His supporters were narcissists, we were told, or naive, or both. Supporting Corbyn was just another form of “virtue signalling” on social media; of showing off how worthy and right-on you were.

As it was, it was Facebook, not Twitter that dropped the biggest hint. People my own age and younger, on Facebook, who seemed suddenly excited about politics, either for the first time since we had marched against student fees and scrapping the education maintenance allowance, or for the first time in their entire lives. Some actually went so far as to join the Labour party, or to sign up as supporters so they would have a vote.

When I spoke to some of these young Corbyn enthusiasts in July, my suspicions were confirmed. They were furious about austerity and generational injustice, annoyed at what they saw as patronising media coverage of their concerns, and disillusioned with the political status quo. Many my age had their politics shaped in the shadow of the Iraq war, whether they were old enough to march against it or not. Those younger had seen their education become a commodity under the coalition and social and generational inequalities widen. Corbyn offered hope and was, as I wrote at the time, “scratching a persistent anti-Blairite, anti-establishment itch”.

More than six months on, it’s difficult to deny that Corbyn has reshaped the Labour party, and almost doubled its membership. An investigation by this newspaper found that university towns and cities recorded some of the biggest membership rises, reflecting this influx of young people, and predicted that there might be a clash coming between those who wanted to conduct politics the same way they did 30 years ago, by “sit[ting] around calling each other ‘comrade’ and ‘Mr Chairman’” and the new, younger members who, some suggest scoldingly, aren’t bothering to turn up to meetings.

Then again, why should they? The group Momentum was set up last year to galvanise the passion of those who rallied in support of Corbyn during his leadership campaign, and is extremely active on social media. It has an estimated 90,000-100,000 supporters, many of them young, who have pledged to defend Jeremy Corbyn should he face a leadership challenge. We hear much about how Corbyn represents a new way of doing politics, and this new attempt at a mass leftwing social movement is certainly different. It’s also true that not all Momentum members are especially interested in attending a never-ending series of meetings.

In a pub in London’s King’s Cross, Santiago Bell-Bradford, 24, describes them to me as “tedious” affairs involving motions and countermotions and, worst of all, points of information – a “guaranteed” way of killing anybody’s passion. Vyara Gylsen, 28, has never been to one. Beth Foster Ogg, 18, is involved in People’s PPE – a lecture series that aims to share knowledge from Oxford PPE courses with “ordinary people” – and is quick to point out that just because young people aren’t interested in meetings doesn’t mean that they are not political. This notion – that Generation Y tends to be less interested in party politics than in issues and ideas – is still something that politicians struggle to get their heads around.

Facebook Twitter Pinterest Members of Momentum at a meeting in Whitechapel, London. Photograph: Andy Hall/The Observer

Everyone Foster Ogg knows is “doing politics” in one way or another, whether through volunteering, blogging or getting involved through their schools and mosques, and there is evidence to support this view: a report last year found that, far from being apathetic wasters, young people do the most hours of volunteering of any demographic.

This youthful enthusiasm for Corbyn seems to indicate that young people aren’t as disengaged with politics as first appearances might suggest, but Generation Y are hardly giving the baby boomers a run for their money. A large proportion of them (42% of those aged 18-24 in May 2015) don’t bother voting, a statistic that is unlikely to be improved considering the new voter registration measures. Their voices are all but absent from key debates such as that surrounding the EU referendum, a particularly dry example of a political debate that offers little to pique young people’s interests. However, a disaffection with mainstream politics does add credence to the argument that Corbyn’s popularity might be because, despite his age, his way of doing things appears fresh and different.

One of the main turnoffs for younger people – and I have felt this myself – is the perception that politics is an exclusive club, not to mention the level of prior knowledge that seems to be required from much political coverage. Gylsen joined the Labour party because of Corbyn and is a Momentum East End delegate, but tells me with a slightly shamefaced look that, after Corbyn won, she had to Google what the term “shadow cabinet” meant. (I can just imagine the facial expressions that some bubble-dwelling political nerds will make as they read this). To hear her talk about how pleased she was to be voted in as a delegate “despite” her background does hammer home how Momentum’s inclusive stance differs somewhat from the stereotype of privileged, metropolitan young leftwingers that is so frequently described.

These particular members might be Londoners, but they are no different from their fellow young people in communities up and down the country (there are Momentum groups everywhere: Hull, Truro, Carlisle, Nuneaton). In fact, I would argue that the grassroots nature of the organisation is part of its appeal. There is no denying that young people have felt the brunt of government cuts. While Gylsen may not have known what a shadow cabinet was, she says she knows what it is like to be from a low-income family, knows about house prices and about what is happening to youth services. Isn’t that sort of engagement what politics ultimately means?

There’s no doubt that the young people who voted for Corbyn feel patronised by a lot of the media, a stance that is hardly going to get them reading newspapers. What this means for them as potential voters remains to be seen (will their passion translate to the ballot box?), but giving them some intellectual credit is a good starting point. This is the mistake that mainstream politicians and media commentators have made: their focus is on Corbyn and his perceived electability, when to the young people who voted for him it isn’t really about Corbyn at all. It’s about the ideas and the hope that he represents, which has been bubbling under the surface long before he stepped up, and I have no doubt will continue to exist after he is gone.

If Labour wants to appeal to more younger people, then getting behind their leader might be a good start. But let’s not fool ourselves that this is all about Corbyn. If Generation Y really are shallow, selfie-and-status-obsessed morons, then a 66-year-old backbench pacifist is hardly the cutting-edge stuff that memes are made of, yet he’s a surprise social media hit. Can this really be all down to virtue signalling? Whatever it is, it doesn’t seem to be an attempt to look cool. “Young people are not jumping on some bandwagon,” says Foster Ogg. “There’s more going on. They are identifying with his ideas. Otherwise they wouldn’t support some old white man with a beard.”

In other words, without Corbyn and his beard, the acute sense of injustice felt by many of his supporters would not just hang in the ether – it would find another focal point, just as it is doing so across Europe and in the United States. It just so happens that the ebb and flow of politics over the last couple of decades has meant that the pre-New Labour lefties are getting on a bit, and the post-New Labour lefties aren’t old enough yet. They may not be at all the meetings, but nonetheless they are there, waiting for their moment. We can be sure of that.