Just because they make tens of millions of dollars doesn't mean that they're the ones holding the pursue strings. For every 10,000 Spielbergs, Eastwoods, and Weinstein's there is one Les Moonves type who actually calls all the shots. The employees are overwhelmingly liberal. The employers, not so much.

Besides, most actors/directors/producers dont make nearly enough money to have the impact of a Koch or Mercer.