Ah, OP's assertion was the price is crazy from retail investors, which i assume would be non-institutional, non-insiders. It's impressive that a few % of owners can double the share price. Unless, they meant Musk was buying shares at $350+
I mean, I don't think that is what is happening right now, but you might be surprised what it takes to move a market sometimes. The Flash Crash[1] was caused by a single individual. Granted he was playing with futures and you can get some insane leverage with a modest account there, but it is within the ability of a couple of individuals with six-figure accounts to make some well placed bets and move a market significantly.
He definitely set off a chain of events that caused automated market makers to re-evaluate their idea of a fair market value rapidly in the downward direction, and it cascaded from there.