There is a famous story about the great 19th-century statesman Gladstone on the campaign trail. During one of his trademark three-hour speeches, a little girl posed a question to her mother. “Mummy,” she supposedly asked, “what is that man for?” Since Twitter appeared in July 2006, people have asked the same question about it. An incredulous Daily Mail asked it and received no satisfactory answer. I mean to say, what possible utility could attach to a service enabling people to publish 140-character “tweets”? The very word tweet suggested that the thing was a geeky joke, an online toy that the founders created simply because they had the free time and the resources to do so.

And now? Twitter has become the medium of choice for the most powerful man on Earth, enabling him to boast last week about the size of his “nuclear button”. There is even a Twitter bot – an automated script – @RealPressSecBot – that takes each Trump tweet and reformats it as a White House press office statement.

In a way, it’s no surprise that Trump should have taken to Twitter because it has the right bandwidth for his thought processes. Technically, bandwidth is the range of frequencies that a particular communications channel can transmit. The wider the bandwidth, the more information the channel can handle, which is why analog phone lines were OK for voice communication but hopeless for relaying music. Smoke signals are one of the oldest communication channels devised by humans and they were very good for communicating danger or summoning people to gatherings. But as the cultural critic Neil Postman once observed, they were lousy for philosophical discussions. The bandwidth is too low.

Q&A What is a Twitter bot? Show Strictly defined, a Twitter bot is any automated account on the social network. That can be something as simple as automatically tweeting links to news articles – most of the Guardian's social media accounts are technically Twitter bots, for instance – to complex interactions like automatically generating Emoji-based art or automatically replying to climate change deniers with scientific evidence. But, as with "troll" and "fake news", the strict definition has been forgotten as the term has become one of political conflict. The core of the debate is the accusation that a number of political tweets were sent by "Russian bots", with the intention of subverting political debate, or simply creating chaos generally. Based on what we know about Russian information warfare, the Twitter accounts run by the country's "troll army", based in a nondescript office building in St Petersburg, are unlikely to be automated at all. Instead, accounts like @SouthLoneStar, which pretended to be a Texan right-winger, were probably run by individuals paid 45-65,000 rubles a month to sow discord in Western politics. In other ways, they resembled bots – hence the confusion. They rarely tweeted about themselves, sent far more posts than a typical user, and were single-minded in what they shared. People behaving like bots pretending to be people: this is the nature of modern propaganda.

Same goes for Twitter. It’s great for transmitting news tersely, which is why an increasing amount of breaking news comes via it (and not just warnings from Trump about supposedly imminent nuclear exchanges, either). Once upon a time, governments and corporations with important announcements to make would issue press releases to the major wire services (Reuters, Associated Press, Agence France-Presse et al), which would then relay them to their subscribers. Nowadays, the first alert comes via a tweet.

When Twitter started, it was this newswire capability that struck me. It seemed a genuinely democratising development – citizens could learn about breaking news at the same time as editorial gatekeepers. And the barriers to entry for users were so low: people who would never have been able to muster the self-confidence to publish a blog could just sign up and contribute their twopennyworth to the public sphere.

Which they did, in large numbers and with very mixed results. The narrow bandwidth of the channel accounted for much of what happened. The 140-character limit turned out to be good for expressing outrage, abuse, fake news and jokes, but hopeless for civil discourse. And it became clear that Twitter was critically vulnerable to automation: an increasing proportion of its users were bots rather than humans, which made the service particularly useful for political actors of all stripes. Some researchers now believe that up to 50% of traffic on the service is generated by bots.

Initially, Twitter was a joy to use. If you were careful about whom you chose to “follow” then it was like eavesdropping on the zeitgeist. But as it grew it became more and more irritating: one’s feed became choked with inane retweets and demonstrations of the astonishing solipsism of users who saw the service only as a vehicle for self-promotion.

What was most distressing, though, was the way Twitter seemed to release people from the norms and constraints that govern behaviour in the physical world. The waves of hatred, prejudice, racism and misogyny, especially directed at women who were prominent in public life or in cyberspace, came to be beyond endurance, at which point many of us simply decided to disengage from the platform. One of the (many) downsides of Trump is that he has more or less obliged journalists to go back to monitoring their Twitter feeds, which also allows him to drive the news agenda in a way that few other democratic politicians have ever managed.

If there is one piece of good news in all this, it is that Twitter can be regulated. We saw this when Lord McAlpine’s lawyers came up with a brilliant scheme for punishing Twitter users who had thoughtlessly or maliciously retweeted defamatory material about their client. And last week a brace of far-right German politicians had their accounts suspended under a new law banning hate speech on social media. So maybe there is light at the end of this particular tunnel.

I certainly hope so. Although Twitter is the Cinderella of social media in terms of profits and users and is still struggling to find a viable business model, we would really miss it if it disappeared. And so, of course, would Donald Trump.