I noticed that the mainstream hasn't fallen too much. At 5 o'clock, when most people are sleeping, the altcoins are likely to experience a short-term liquidity drain, triggering a chain explosion.

Algorithmic trading estimates that this wave of losses is huge, those who placed low price orders in advance probably had a good time.
The reason is simple: at times like this, the bn is bound to crash, and without any buying pressure, it naturally falls in a chain of sell-offs.
The US stock market has fallen by 2-3%, and the A50 has dropped by 4%. Based on historical data, it is reasonable for Bitcoin to normally drop 10% and altcoins by 20-30%.
Exceeding this value, a large number of spikes can only be said to likely be caused by network issues combined with a lack of buying pressure.
From a conspiracy theory perspective, if it is man-made to achieve such an effect, it is likely to attack exchanges and create network congestion.