"If the following 25 players in the world where all 2800+ Carlsen would already be 2900+."
Why are you assuming that Carlsen would always win against other players if the other players are that much stronger? Maybe if the following 25 players were all 2800+ then Carlsen would take more losses.
Because, as already explained elo measures relative strength not absolute one. If he's a better player he's going to beat them more often than not while not losing all the points he does now for drawing.
Why are you assuming that Carlsen would always win against other players if the other players are that much stronger? Maybe if the following 25 players were all 2800+ then Carlsen would take more losses.