They skew left because their bosses in Hollywood are left. If they go against the flow they don't get acting gigs. Remember Gina Carano?
If Hollywood bosses were rightwing you can bet your ass that actors and actresses would also be. They are basically cowards and not as courageous as they try to make themselves out to be.
Sure it's not universal, hence the skew phrasing. There are a few outspoken exceptions eg. James woods, Gina, and some who did not speak up for fear of being cancelled absolutely, but for the most part the majority truly do believe the nonsense they frequently spout, look at Alyssa Milano and De Niro for example, they absolutely mean it
The very premise of acting is to escape into a fantasy world where you are someone else: that has greater appeal to a certain personality type. The ones that make it as hollywood stars just tend to have better cheekbones than most of the others that remain serving in restaurants year in year out
Certain vocations always draw certain people with certain personalities and brain wiring, actors/artists are no different in that respect. No knock on John Lennon as an artist but look at the lyrics for Imagine: utopian platitudes for the most part in relation to the real world we inhabit, a fact he even effectively partially acknowledges in the chorus