I'm sure plenty of funds would invest with him. I'm not sure why you're so sceptical.
Okay, which ones? I’m not aware of a funds that would write 10 billion dollar checks (and you would need multiple funds to get to the necessary cash).
I work in the space and all the funds I’ve seen have limitations on the size of a particular investment so no fund is calling all their capital to hand it over to Elon. Besides, if you can’t use leverage, it would absolutely kill their returns. And for what, Twitter??
The only possible way I see is to get one of the Middle East sovereign wealth funds (who actually can write a 50 billion dollar check) but the chances of that happening are laughable.