I think a lot of people say they "believe" that, but really the question they are answering is, "do you like Bill Gates, or do you think him morally capable of doing this horrible thing?" Bill Gates was one of the early, big proponents of Common Core, and educational testing and reform movement which ended up becoming very unpopular on the right.
That’s a massive cop out. You either believe in conspiracy theories or you don’t. People who don’t believe in conspiracies don’t say they do as a way of expressing they don’t like the people involved.
In my experience, your second statement is, factually, incorrect. Nothing personal, but I find that not to be an accurate reflection of human behavior.