- it's actually to get regulatory capture
- it's hubris, they're trying to seem more important and powerful than they are
Both of these explanations strike me as too clever by half. I think the parsimonious explanation is that people are actually concerned about the dangers of AI. Maybe they're wrong, but I don't think this kind of incredulous conspiratorial reaction is a useful thing to engage in.
When in doubt take people at their word. Maybe the CEOs of these companies have some sneaky 5D chess plan, but many many AI researchers (such as Joshua Bengio and Geoffrey Hinton) who don't stand to gain monetarily have expressed these same concerns. They're worth taking seriously.