I could almost guarantee that this was caused by Binance removing exchange fees off BTC/USD trading pairs.
Last time this happened the exchanges that had zero fees were laundering a lot of money that eventually forced the authorities to kick their doors down and shut them down for good. I wonder if Binance is on the same path and if they are close to being shut down.
The purpose of this is to encourage traders to make more trades during bear season, but it won't last for long. By doing this, Binance will gain more reputation and attract more users, but since it is not profitable for them, they will end the program.
Binance is the only exchange not cutting staff this bear season and they are working hard to recruit staff and expand their market, with what CZ is doing binance deserves to be the largest exchange in the world.