You are correct that ESPN is one their biggest revenue drivers. The issue is that ESPN and to a certain extent even ABC operating margin is at a negative 8-10% variance year over year and it's not getting better forcing other units to pick up the slack.
They need to invest their money on the areas with a positive variance. Parks, movies, etc. And reduce costs in their TV area.
But I am just a bean counter and not in Iger's position.