I think the main reason is the sharks in the crypto market. They have the power to decide the price of the altcoins. So they can make a lot of profit from the trading and increase and decrease the price of the altcoins. They make small traders fear because of the cost of going down and forcing them to sell all their coins to secure their assets. and the sharks would buy all the coins at low prices and sell them at high prices.
I have the same speculation as you. This is the only reason I know why the market keeps on going down nowadays. The whales have the right and still continue to manipulate the prices of the cryptomarket. Though in the recent months, I was able to read some articles about the fall of bitcoin and the reasons is sometimes the lack of support. Example is the banning of cryptocurrencies in different countries. Another reason that I read is the regulation of cryptocurrencies continues in some countries.