You don't need to ask Elon Musk how to fix Twitter. Elon may know some things about rockets, but aside from that he will only give you bad advice. He is not the average Twitter user and doesn't experience what most of your users are experiencing.
I am glad that you have come to me for a second opinion. I appreciate you taking time out from your busy schedule. Giving all those fascists blue ticks must take up a lot of your time. So here's what you need to do:
First, take a long hard look at your bank account and any other assets which you may have. Ask yourself "can I live modestly on this for the next few decades, or indefinitely? Do I personally have enough?". I think I know what the answer will be. Then ask yourself "do I really need the money, or am I embarked on a more general project to do something for the world?". To "put a ding in the universe", as the late Steve Jobs put it.
It's going to be the latter.
So how to improve the world with Twitter as a starting point. You won't be able to fix any of the existing problems with AI. That will only make the situation worse. Turn Twitter into a set of fediverse instances. You could do it by country/state (twitter-uk, twitter-us-ca, etc) or by topic, or both. Country is probably easiest, since the user migration can be automatic. Go all-in on ActivityPub. Send some people to W3C to fix the protocol specification to properly include all of the features actually in use in the current fediverse. You don't need to be a genius or invent anything new. It's all been done for you already. All you need to do is produce a nice document which is easy to read, with examples. Then turn your company into a non-profit foundation which maintains the instances and contributes to the evolution of open standards.
You may be wondering how this solves the "fake news" or bot armies problem. It doesn't. But if you implement the federated standard with all of the moderation controls, and let admins do their thing, then you will find that the bad actors become contained. They lose their global reach and ability to mobilize rapidly. In a federated system the problems that you're trying to fix become more tractable. Users can migrate around to whichever instance suits them and there's a self-organizing "invisible hand" type of effect. New spinoff instances will appear and some of those you originally set up may fail, but that's ok.
You can spend the rest of your days as an ambassador for open standards, an open web and instance governance best practices. This is how you put a ding in the universe. If you just carry on the way you are doing things now then you'll go down in history as "the guy who helped rig elections" or "the guy who helped give nazis a platform". I'm assuming that's not the sort of legacy you'd prefer to leave.