It's networking, plus the fact that they often own their own production companies, plus the ability to portray a younger role well into their 50s. Brad Pitt is older now than Marlon Brando was in The Godfather.

You have a lot more professional options if you can pull off a younger character.

Because it's bullshit. They're bankable stars in an era where bankability is key (ie. superhero movies).

Their production companies exist as a vehicle to get a piece of that pie and have more creative control.

ISTR lots of articles around and since the turn of the millennium about the TV/Film desirability gradient starting to reverse, at least for people not already at the pinnacle of movie stardom, with young actors with modest early career movie success actively working to love to TV, rather than vice versa.

EDIT: And, though less frequently, I've seen similar things for other jobs in making filmed entertainment, with TV getting a lot more respect as a medium for storytelling.

yeah, I'm sure the networks were as strong or stronger since hollywood became a thing