we all know no one can controls the bitcoin price because bitcoin isn't like bank, stock and valas. but if the whales owned 51% of bitcoin, can do it?. if happen, does decentralization not exist?
I think you are confusing two things.
One is a whale where a trader who holds a huge amount of coins trying to manipulate the price and benefits from price difference.
The other is 51% attack which is done by miners owning more than 51% mining power and tries to attack the blockchain.