Bernie ran F1, in the end, to make as much money for himself as he could. Liberty Media saw Bernie become a billionaire on the back of F1 and want a piece of it.
Don't get carried away that these Americans, with their bizarre facial hair and bonhomie, are here to be altruistic and run the sport for the benefit of either the teams or the fans, it's a cash cow which they will milk until it has dried up and then they will toss it to one side and move on to the next one. Oh, and the man who owns all this is described on his Wiki page as being a "Libertarian" so expect nothing unless you pay for it.