In most centralized entities, interests are conflicted. With mining, the value of the income is directly determined by the price of the cryptocurrency.
There are other incentives beyond most obvious ones. E.g. hijacked miner could attack to pump another currency (crypto/fiat) the miner holds.
Incentives are out of equation when you speak of fault tolerance. Incentives are not calculatable. Only "tolerance" (# of tolerable byzantine nodes) matters. And that's 2 for eth and btc. TWO.
Why would you want to mess with your underlying cryptocurrency and threaten your income if you're a mining pool?