Don't get me wrong, I think what they're doing is very cool, but how exactly has SpaceX created a public good?

Drastically lowering the cost of access to orbit, potentially providing affordable worldwide internet coverage with performance that isn't dogshit, providing competition for terrestrial cable and traditional satellite networking companies.

If one day we do end up with colonies on the Moon and/or Mars, historians will point to SpaceX's drastic lowering of the cost of making it to orbit as one of the critical stepping stones that made it happen. Not only does it directly make such things more possible, but it increases the amount of economic activity that can occur in space, which grows the entire industrial ecosystem and indirectly unlocks even more possibilities in the long run.

Internet in the rural parts of the world is being revolutionized.

It's because the guillotine has transitioned from "something my aristocrat grandparents were afraid of" to "ancient history".

I believe we are close to saturation of how many museums and universities one can have without them feeling empty.