What happened in the parliamentary elections last week was the political equivalent of the collapse of a financial bubble.

For two years, practically everyone outside the circle of Jeremy Corbyn’s own supporters has been insisting the man was “unelectable”. He was an extremist, a well-meaning incompetent, a dogmatic Trotskyist pacifist whose vegetarian beardedness would drive millions of hard-drinking, meat-eating, working class voters into the arms of the Tories.

Corbyn’s election to the Labour leadership, we were repeatedly told, would mean the party would be out of power for a generation. Instead, he’s caused the biggest swing to Labour since 1945. They’ve invented football chants about him.

Everyone is now scurrying around to answer the question of how they all got it so wrong, but almost no one is asking about the concept of “unelectability” itself. How did we get to the point where the candidate of a major party was judged not by his political vision, programme or sensibilities, but by an estimation of how different classes of imagined voters were likely to respond to him?

How is it that this has become our basic standard for judging politicians? And by “we” I am referring not just to political junkies, professional or otherwise, but to the electorate as a whole.

I remember looking through the comments sections of articles on Labour’s prospects last year, and being startled that almost every single person emphasised not what Corbyn stood for – those who did mostly claimed approval – but rather “electability” issues.

No one would vote for him. Therefore, there was no point in voting for him. The remarkable thing is that there were thousands of these commentators. Collectively, they were a substantial chunk of the electorate. And here they were saying they wouldn’t vote for a candidate whose views they agreed with because they assumed no one else would.

Back in 1936, John Maynard Keynes suggested that financial markets were organised a little like a beauty contest – except, he emphasised, a beauty contest with one important twist. Imagine newspaper readers were shown a hundred portraits, then asked to judge not which face was the prettiest, but which face everyone else would think was the prettiest.

In that case, everyone would not only be trying to imagine everyone else’s preference, they’d really be trying to guess what everyone else guessed everyone else’s preference would be. And so on, ad infinitum. This, Keynes argued, is basically how the financial sector works. Second-guessing of this sort can lead to crazy bubbles when people bid up, say, tulip bulbs in 17th century Amsterdam, or housing in London today, just because they think others want them.

In between Keynes and the latest general election, the financial sector itself has come to dominate the world economy – and British and American economies in particular.

This rise has been accompanied by a profound cultural shift. Starting in the Eighties, when news feeds began to provide stock quotes moving along the bottom of the screen, everyone in rich countries has, in a thousand subtle ways, been encouraged to look at the world through the eyes of an investor.

The same period saw the rise of punditocracy. Even in Keynes’s day, newspapermen were notorious for their cynicism (think of the movie The Front Page). But in recent decades, that particular strain of cynicism – the assumption that politics is really just a game of personalities, showmanship and manipulation, and in no sense a battle over values or ideals – has migrated from the Fleet Street pubs to newspaper comment pages, and from there to news stories, and from there to anywhere anyone argued about politics.

You can trace its rise by looking at the history of the word “unelectable” itself.

For the rich and powerful, popular cynicism is extraordinarily convenient. It’s no longer necessary to convince people that the political or economic system is fair. All you have to do is convince them everyone else thinks it is.

It’s all a little like those tabloid newspapers they sell at checkout counters in America, full of fake stories about aliens and haunted toasters. The trick isn’t to make the reader believe the stories. It’s to fool them into believing other people believe the stories – so they can go home and laugh at a bunch of imaginary idiots without realising they’re the idiots themselves.

Donald Trump has taken this particular variety of scam to perhaps its ultimate point of artistry. He more or less gave the game away during a victory rally on 9 December 2016, when he mentioned Hillary Clinton and some of the audience began chanting “lock her up, lock her up.” No, no, he said. “That plays great before the election – now we don’t care, right?”

In other words, he addressed his entire audience as if each were part of his team, even if the only people they could have been trying to influence in a case like this was one other. This helps explain why Trump supporters remained unmoved on learning fake news was fake. They didn’t see themselves as suckers believing made-up stories. They saw themselves as part of the team purveying and disseminating those stories.

All this recalls the South Sea Bubble of 1711, where “every fool aspired to be a knave”, buying up worthless financial instruments for extravagant prices hoping to pass them off to the next sucker at a profit before the inevitable collapse.

When bubbles burst, the results tend to be dramatic. Corbyn’s sudden rise can be seen as another’s sudden fall. What we have just witnessed can, I think, be legitimately referred to as the popping of the Blair-Clinton bubble. That is, the ending of the assumption that a tepid, compromised, market-friendly, bureaucratic centrism that nobody actually liked was the only form left-of-centre politics could take, because everyone was convinced that everyone else thought so.

The moment a credible player appeared on the scene who rejected the underlying assumption, everyone realised no one really much liked it to begin with – which is, is of course, why the entire political-journalistic class united for two years to try to convince us that the player in question was not credible.

The only remaining question is: has the bubble fully collapsed? How far will it go? Will this spell the end of the financialisation of politics? If so, what does it tell us about the ultimate fate of the financial bubbles on which it is founded?

David Graeber is a professor of anthropology at the London School of Economics and the author of Debt: The first 5,000 years