Don't forget the fact that all these companies built their empires on top of "viral growth", which is an effect only possible because they figured out a way to get people to spread the "idea" of the product the company was pushing at the time to others. Of course, making money off these ideas is also important, so the VCs and private equity firms were there to help "guide" the company into making decision to change the product in ways the users don't/won't/can't notice.