Already in many sources they explain:
1. Power outages in the Chinese province of Xinjiang, which led to the loss of many industrial miners from the network, began on Friday, but this effect fully manifested itself later.
2. At the same time, there were still unconfirmed rumors that US regulators may start an investigation into unnamed large financial institutions for money laundering in cryptocurrencies. This led to a panic in the market and a massive liquidation of positions on the exchanges. Bitcoin was above $ 62,000 on Saturday morning, and set a local low of about $ 51,500 early on Sunday morning.
Do not forget that the higher taxes (much higher) on the rich also became a problem for the crpto people who sold and profited right away so they can pay the current tax rate on their income before the new tax rate comes. If you profit from crypto right now you pay %30 tax rate and if you do it after the new tax comes in that is 43% that is a lot of difference.
Considering this works for 1+ million dollar profits, that means that many very rich people realized their profits now so that they can reenter later on with whatever they want or maybe not even reentered the market. That is a reasonable approach, if I had that much money I would have done the same but I believe I will never own 1+ million dollars in my life, unless something shocking happens it is not going to happen. This is why I think it is obvious that this played a role, not saying that was the whole thing, but it was one part of it.
Since this tax plan has such an uncertain future, I have trouble believing this is the reason bitcoin fell so dramatically. Who would sell an investment they believe in because a tax plan that is, at best, unlikely to pass was proposed? Further, the stock market didn't have a sell off of a similar magnitude, so it's unlikely this is rich people trying to lock in gains at a lower rate. If so, you would have seen a similar sell off in stocks.