Reached their limits? That doesn't explain the poor performances towards the end of his reign compared to his first season. After that time their should have been a move towards being able to make the players comfortable moving the ball around - It was a Martinez built side that was humiliated at Big Sam's Sunderland.
It seems strange that Martinez took his 72 point side and then made them less comfortable with the gameplan and less able to cope with the atmosphere at Goodison which in truth is often more sedate, quiet and apathetic than genuinely toxic.
Do you believe that his in game management, cartoonish positivity, and sometimes poor recruitment had less to do with his downfall?