Elon is an oligarch plain and simple. SpaceX is impressive, and I'm a big fan of NASA's research, but let's look past the marketing of him trying to save the human species or whatever.
I do think humanity may have to settle another world (or move to a post-biological existence where we can just park our satellite brains around a star for energy), but this is going to take a lot of scientific advancement over many centuries. Elon's plan would make a lot more sense if Mars was an Earth 2.0 and we just needed to move a bunch of people there, but it's not and even if we do find something really close to Earth with JWST, it would take centuries to get there. In short, our best approach is to save the planet we already have and continue funding scientific research.