Elon is a sick person. Keep that in mind whenever you consider anything he does or says. Twitter was a nice place to be - the site worked smoothly and there was reasonable regulation to keep the vermin under control.
But Elon *wanted* the vermin because he agreed with them, and it didn't matter if 99.9% of the users don't want to have Nazis on their feed. He did and he had the cash to shape the place to be a reflection of his own sickness.
As for fixing up the place, I don't think he really cares. He doesn't look beyond the noise and if a lot of people are saying (and liking) the filth inside his own mind, that's good enough for him. Free Speech was the excuse, but Twitter has become a bigger megaphone for the crazies than Truth Social and the rest of the old-school social media sites. That's a huge win for him, because when you have more money than God, all that's left is the illusion of everybody adoring you.
Twitter is now massively devalued because advertisers can see the state of the place and don't want to invest in advertising, or even being on there at all. And social media is all about advertising. Look at the advertisements now compared to before Musk took over. Twitter is in a spiral and so long as the place is mainly known for being an outlet for hate and stupidity, it's just going to get worse, and value will continue to fall. And all the blue checkmarks in the world won't change that.