I fully agree that part of his motivation is self amusement. It's one of the things I really like about Musk, is that he's clearly still connected to his inner child, and I think that's part of what keeps him dreaming.

I think the people most offended by it tend to be the people who have lost that joie de vivre and miss out on the fact that we're all just existing here and now. Sure, do the very serious things that need to be done for a person with his resources, but in the end, we can't even prove it's not all just a damn simulation can we.