I see a lot of topics talking about why bitcoin did this or that. Sometimes there are clear indicators as of why but many times it simply happens. Coincidence, trading bots and simple TA can affect the price and create a snowball effect easily.
Imagine 3 whales with 1000 btc each decide to sell bitcoin and by chance they do so at the same time. Of course the price will tank and people will wonder why, bots will follow and so on.
I agree that Bitcoin is heavily manipulated. Rather the whole cryptocurrency market is heavily manipulated because of the lack of monitoring authority. But there is always some reason that kick starts the fall which then gets heavily manipulated by the whales for some quick profits. Like recently, the not so expected response from the bakkt lead to the fall which then intensified because of the manipulation. But they too don't play badly with the market as they can't make retail traders leave the market because of the excessive losses.