Probably it was just supply and demand thing in the market, bitcoin was recently just pumping in the past month so most of the people are already expecting a correction at this point.

There are some articles about a million bitcoin sell of in the market, its already too risky to hold bitcoin at this point if your not going for a long term investment since we already have a big resistance at 40k$.

Also according to some research majority of the investors think market is already in a bubble, personally i think market is already at its limit and needed some correction at this point. There are also some negative news about bitcoin that could affect the market like this double spending thing:

https://markets.businessinsider.com/currencies/news/bitcoin-price-double-spend-flaw-critical-report-suggests-2021-1-1029990921