Tesla
1) $TSLA was overvalued based on unrealistic assumptions about competitors and Tesla's ability to stay on top.
2) $TSLA was sort of a meme-stock that has just run out of comedy runway.
3) $TSLA is now a meme-stock and ordinary investors don't generally want to hold meme-stocks.
4) Investors are genuinely concerned about the behavior of the Twitter CEO, who as we all know is the Tesla CEO. Is it really surprising that making bad decisions in one arena will affect outcomes in another?
I have no idea which if any of these are true, but they all seem somewhat plausible. Really, each of these plus more are probably contributory factors for different investors.
Meta
1) Social media as a profitable enterprise has not especially proven durable over the long term. Plenty of entrenched incumbents in all sorts of industries fail after decades or centuries even. Meta is running out of good ideas. (Again, just my guess.)