I`m pretty sure that most of the miners don`t care about bitcoin,they care only about their profits.
If they can make more profits with some shitty altcoin,i`m sure that they would leave bitcoin immediately.
The "divide and conquer" strategy won`t work against bitcoin.
Proof-of-work: miners' interests are not aligned with interests of users. They are two different groups of people.
Proof-of-stake: users hold tokens and secure the network with the staking power of tokens. They are the same people.