As you can see on https://www.f2pool.com/coins other coins using SHA256 as PoW algorithm only amount to about 1% of Bitcoin's daily dollars of Pow Produced, so
if any nontrivial amount of hash moves there, then those will soon become unprofitable too.
Yes, but the coins with less participation require less power to compete. To make a market argument that there is an equilibrium of players across all coins, implies there are actual individuals finding opportunities and switching coins when they get out of sync.
