I think miners acting in their self interest would realize that a much larger number of transactions with smaller fees would result in a larger total fees profi

I think miners acting in their self interest would realize that a much larger number of transactions with smaller fees would result in a larger total fees profit per block solve. Almost all of their resources would be the same - the vast majority of their electricity bill is spent solving the block hash compute problem, the resources to actually process the transactions and send them are small compared to that. The basic logic holds, that you cant make money if nobody uses Bitcoin.