What is the motivation behind the money? Why are they really doing this?

We want to colonize Mars and maybe the Moon, not because it is easy, but because we have a mistaken belief that it is easy!

Asking “Cui bono?” will get you most of the way to an understanding of what’s going on… but sometimes there is no benefit, and rich powerful people are just acting on mistaken assumptions. Like, the assumption that a Mars (or any other body in the solar system) will take anything less then slow grueling highly sophisticated intricately organized staggeringly terribly carefully coordinated work for like 12 human generations.