There were two main theories I saw.
One was that mining rates dropped due to flooding in China which temporarily took out ~10-30% of the total hashrate.

The second reason was due to a funding rate indicator on leveraged positions that said there were a lot of longs open and a high funding rate for shorts (meaning short term shorts were paying people to open them and leave them open). I assume that could then build into a bias if the market starts to get a bit stagnant.