I think we can state as a truth that they have less potential profit.

That’s true but it’s not because people aren’t playing single player games. The reason single player games are less profitable is because the non-subscription, non-microtransaction single player market is extremely saturated with indie games. That makes it very hard to sell AAA single player games. The standards are extremely high and the opportunities for extra monetization are not there.

I have been a single player gamer for most of my life, yet I haven’t bought a AAA single player game in decades. I have more indie single player games to play than I know what to do with, and frankly they appeal to me more than AAA titles. Expensive graphics and voice acting don’t have much draw for me these days. I am much more interested in roguelikes and retro games now.