Nobody left on that platform is going to be convinced of anything anymore.
I'd beg to differ. Although it's true that the ratio of neo-Nazis and generally just far right freaks has far surpassed the number of everyday people, that doesn't mean those people don't exist anymore.
I always bring this up in conversations about leaving social networks, because if you don't understand it, it will warp your entire perspective of why people stay on shitty platforms in the first place. The Network Effect is what keeps people hooked on these platforms, even when the owner becomes a literal neo-Nazi.
The people who have already left are the ones that are capable of and willing to sacrifice the scale, reach, and history that Twitter has, in the hopes that whatever platform they move to will treat them better. Leaving Twitter means deleting your digital history, erasing every connection you've made on the platform, and entirely cutting all of your messaging off from anyone who hasn't yet left.
AOC is already on alternative platforms like Bluesky, so people who are willing and able to move, that would otherwise have stayed solely because she was still on Twitter have already done so. The people that remain do not remain because of her, they remain because of everybody else.
Yes, there are still quite a few neo-Nazis outnumbering the average person on there, but there are still quite a few average people that are still on Twitter. Don't forget that the average person doesn't seem to care when the companies they buy products from exploit child labor, fund wars that keep oil prices low, and suppress the wages of the workers in their own communities. The average person simply does not have the will to sacrifice what they must give up by leaving a large platform like Twitter, so they remain there.
If AOC didn't benefit politically from being on Twitter, then she would have entirely left and deleted her account a while ago.