Either you gain a bunch of power or you lower the network total hash power. Question is, what does it cost to bribe key employees at BTC.com, antpool and viaBTC?
Even if you manage to lower the hashrate, which IMO is probably impossible to do via bribery, what then? You still have to spend a lot of money on the hashrate, and the tools you bought for the attack effectively turn into bricks afterwards.
Previous 51% attacks on alts were only possible because the tools they used could be repurposed for something else. That won't be the case after a successful attack on Bitcoin. It simply isn't worth doing at the end of the day, no matter what route the attacker takes.