People can collude to get a disrporotionate amount of the profit from a blockchain. The more people collude, the more profit they get, the more rational it is to join them.
This then bridges into traditional 51% attacks.
This then bridges into traditional 51% attacks.
This is not true. Colluders diminish the value of their PoW reward by reducing the trust of all other participants in the system and honest actors have an even strong incentive not to join them. Just a few years ago a mining pool that gained a very large share of the Bitcoin hashrate had members choose to leave -- https://www.coindesk.com/bitcoin-miners-ditch-ghash-io-pool-...
Because Selfish Mining attacks are not inherently detectable, you cannot expect the average user to detect them.
Too many refutations of selfish mining appeal to an oracle. This is an example of such an argument.