Why would it only work in fairy tales? And let's not forget that we assume in order for this work, you (with a group) have such a huge amount of the BTC market that it is possible to influence the price. Of course it doesn't work if you only have 0,1% of all BTC...but lets assume 1-10%. That would already be pretty huge.
In order to work, the price must continue to move in the right direction
after the manipulator has finished buying or selling. Ideally, the manipulator would want to set off an avalanche of stop losses, but there is no way to know if that will happen. The manipulator
loses money if it doesn't. It is very risky, and the bigger the attempt, the riskier it gets.
Does this manipulation happen in the crypto market? There are plenty of shitcoins that have experienced huge pump and dumps, so it doesn't look like a fairy tale to me

Pump and dump is a different story. In this case, the scammer convinces a lot of people to buy a bunch of coins all at the same time. The price goes up and the scammer sells to those people at inflated prices. The price crashes when the buying frenzy stops and everyone wants to unload.