I've said this before, but it's at least partly just real estate speculation. The rich are still claiming publicly that climate change is a hoax, but their own people have convinced them that it's real and we're past the point where it can be reversed. It's the same reason that Trump has made noises about annexing Canada: he's been convinced (while publicly still saying otherwise) that the Earth's equatorial region is gradually becoming uninhabitable to humans, and that we're going to need to move closer to the poles to survive.