People involved with the media and the flow of information, are so narcissistic and stuck-up that they actually think (or thought) that they had total control over what the average person believed, and that they could manipulate their every action. Then Trump ran for president, they threw everything they had at him, and failed. The significance of that to them can't be overstated. I remember just before election night, there were articles being put out by journalists scolding other journalists, saying that 'yes of course Clinton is gonna win, because we're backing her, but shame on all of you for 'letting' things get to this point, that Trump is even a contender for president'.
Trump proved, beyond a shadow of a doubt, that the media DID NOT have control over what the common man thinks, that they WEREN'T able to influence their actions. You can see the effects of this even with absolute nobodies in the realm of media like Nostalgia Critic - When Zootopia came out, he made a video on it where he said that he personally is tired of 'women power' morals in film, but that it's apparently still necessary because 'Trump was still in the lead', and, I quote 'I don't know where all these people [voting for him] are coming from! They're crawling out of caves in the ground!'
This is also why Gamergate became such a huge thing and why the media seethed about it for so long - people rejected their narrative on such a large scale that they couldn't ignore it or dismiss it. It popped the echo chamber bubble they had crafted for themselves where they are the masters and the world their puppets. But Gamergate was confined to the specific realm of games journalism, populated by the rejects from the entire industry, whereas Trump defied the most powerful media figures in the world and got away with it.
And this is why there's been such an immense crackdown on all forms of dissident information by the tech giants and the media. Where once they could shrug it off because they were completely self-assured that they were utterly in control, now that safety net of absolute confidence they had is gone. This is why they're still obsessed with Trump to the point of holding a pointless impeachment trial and trying to send him to prison even though that wouldn't really do anything. Assuming current global society even lasts that long, I guarantee you we'll still be hearing about Trump DECADES down the line.
And, for that matter, this is why Hitler also remains such a boogeyman - the people in power don't care one bit about any war crimes or authoritarianism, they're far worse than he ever was in that regard. The actual reason is because they believed that they had absolute control over the masses, what they believed, and how they lived their lives, and Hitler not only proved them wrong on a continent-crushing scale, he nearly brought down their entire power structure almost single-handedly. From those days on there's been a certain amount of paranoia on their part, and it's why the holocaust keeps getting touted as 'the worst event in history', Hitler as 'the most evil man in history', why the phrase 'never again' is emphasized so heavily in German schools, etc.