[j_shi]

Main reason likely natural down cycle following parabolic run-up. Remember btc/crypto still a global, minimally regulated market driven by and large by unsophisticated retail investors (though pros are increasingly getting in). Domino effect / reflexivity on way up and on way down. Marginal buyer was simply exhausted at some pt, and institutional demand expected to be next big marginal buyer didn't materialize as quickly as people thought.

That said one guess on a trigger for the most recent sell off was that Bitcoin Cash, a fork of "reference" Bitcoin, forked in a bigly hostile way, resulting in two new Bitcoin Cash chains (Bitcoin Cash ABC and Bitcoin Cash SV - for satoshi vision lol) each now with its hash power majority controlled by one group e.g. highly centralized. The market is confronting the possibility that proof of work -- the most widely used consensus mechanism -- is way more centralized than it thought, and way more subject to value destruction from a tiny % of people.