> if it were to become economical and reliable overnight, there'd still probably be a few decades before it replaced enough existing infrastructure to be the primary energy source

Well, hypothetically if nuclear fusion is solved, wouldn't that be the one of these three with the largest incentive to fix overnight?

Solving climate change for the whole world, not just a problem only some niche groups are interested in would seem more pressing than the other two issues (as serious as they are!).