It has nothing to do with being controlled. The more buyers/sellers, the more stable, and that's obvious.
Do you think all the time there are people that loves to buy? Do you think that there are people that loves to sell? You don't understand what I'm pointing out with its decentralization and I agree there is something to do with buyers and sellers but I'm talking about the decentralization.
Do you think you can pump & dump BTC like you can do with an unknown coin? No. It requires much less money to pump & dump a shit coin with nothing in its order book.
I don't know how you did come up with this idea of pump and dump scenario, its given to different types of market there are people who would love to pump their shit but I'm only pointing out with decentralization.