That doesn't happen in Bitcoin. It's possible in small-cap altcoins where supply is highly concentrated.
With BTC, it's difficult to collude across global exchanges. Not only would it require complex coordination and huge amounts of capital, but it requires depositing it with unregulated and nontransparent exchanges. That's massive risk to take on just to move the market.
People say whales crash the market to buy lower. I contend after years of volume analysis that if whales are attempting to do so, they are most often failing to accumulate their coins back.
Here's one whale's story. He sold 30k coins at $300 in 2014 and bought back in 2017: https://www.reddit.com/r/Bitcoin/comments/6d2tp1/i_am_the_bearwhale_uasf_now/