So postmortem analysis of the crash last night is pointing to about 3 things.
First was a coal mining incident in China led to about ~21% of the hashpower of the Bitcoin network going offline. More of a precaution type of thing to inspect equipment and stuff.
Second was a rumor of several large financial institutions being investigated for using crypto to launder money.
Third and most significant was because of the first two the price was going lower and it triggered about ~$10 billion in long margin liquidations. Sounds like a bunch of people were way over leveraged and just got rough ridin' rekt.