I think you underestimate the effect 2016 Russian disinformation campaigns had on social media companies. If Twitter's default policy is "it stays on the site", it's inviting hoards of garbage on the site in early November every cycle. That's pretty bad for its usability and its future, especially since the people who are running in those elections play a key role in regulating it.
Your post works really hard to characterize Twitter employees as "nefarious" "[D]emocratic operatives" who "publicly lied", "broke laws", and engaged in "gaslighting on a national scale", which frankly I think is baseless and unproductive. But putting that aside, it seems to me that the nature of running a communications platform like Twitter is that there's always someone who thinks this about you. The stakes are pretty high, especially around elections. I'm not a fan of social media, in particular I think Twitter on balance has been pretty bad for humanity, but my reasoning isn't that it's particularly good or bad for a given viewpoint (which seems to be yours). I think what they're trying to do is impossible, they will always fail, and there will always be big negative consequences.
For example, Twitter could've let this story ride. But it's not about Joe Biden, it's about Hunter Biden, and there's no vetted evidence of JB wrongdoing. But if JB loses the election because of this, well that's a huge failure for Twitter also. Or they can build a huge investigative unit that competes with all the disinformation bureaus of all the worlds' governments, but that's clearly a losing proposition.
We get a lot of kicks from armchair quarterbacking and our "I would fix Twitter in two shakes with my enlightened moderation policies" (at least one of us got pretty carried away with this and spent $44B to take a swing) wind-bagging, or alleging some mix of corruption and incompetence. They're a pretty good punching bag. But it's worth saying some reasonably smart people have dedicated their professional lives to solving these problems, and pretty clearly they failed. I think this is probably because what they were trying to do, while noble, is impossible. You can't make a global, public communications platform that all the world's dignitaries use that is (reasonably) free of disinformation and acceptable to all major participating parties. Hell you probably can't even do it for just the Republican and Democratic parties, let alone Germany + China.
What you can do is sell out to them over and over again, which is probably what EM will do. Twitter will become a wasteland of propaganda and banal marketing, trading whatever bona fides it has left for exposure on its platform. It's essentially a private equity buyout of Twitter's attention capital. I think the previous leadership team was wise to this, I'm pretty sure EM still isn't (he burned a lot of their attention capital in a 2 day bonfire), but give it a few weeks.