The bottom you think exists is merely what the dealer wants you to see. Take Dogecoin for example; it has been consolidating around 0.4 for so long that everyone believes it is the bottom, and they all start going long.
The actual cost for the dealer might just be 0.1. When it reaches 0.4, they have already tripled their investment. Then, slowly selling off makes you think this level is a strong support, and it just won't drop. When the price hits 0.3, retail investors rush to buy the dip, while the dealer is selling. At this point, the dealer is still making a profit, and retail investors are eagerly taking over.
Just when you think you're about to make a profit, the price might drop again. By the time it hits 0.2, those who entered contracts at that point have likely been liquidated; dropping from 0.4 to 0.2 with a minimum leverage of 2x would have left them nearly wiped out.
At this point, the dealer can still let the price drop, but they will assess the situation to decide whether to do so. If they choose not to let it drop, the dealer will then enter the market and pull the price back up, ensuring they don't lose a single cent while still making a profit!