You cannot deny that our best bet for long-term survival is to get off this planet. Musk is perhaps a rich idiot, as you put it, but at least he has the right vision.
And when such pods are built, and self sustaining technology mastered, what use is mars really? Why not make big self sustaining spaceships? What do you really need a planet for?
Then followed by a plunge in temperature that will be the last nail in the coffin of whatever agricultural capability we have left after most of the civilisation was washed away. It seems difficult for me to imagine how we could survive that. I agree that it probably wouldn't kill of entire species but it would definitely end the modern civilisation and set the survivors back hundreds/thousands of years.
Does having a settlement on mars change any of that? Should we not first create self sustaining pods on the earth? After that, what do we need mars for? Just for access to water, sunlight, protection from radiation, and gravity? Surely, a settlement on a big spaceship would be viable too?
If something like what happened 10,000 years ago happened today, I'm less optimistic about our ability to survive very long. If we were reduced to couple of hundred people back then when we were used to living in the wild, we might go to 0 this time. There are some small tribes of indigenous people in Amazon rain forrest and couple other places who might be better equipped to survive but that is not guaranteed.
I think you are overestimating resilience of our species, we have not yet been tested by any serious cataclysm since modern civilisation, compared to our ancestors, who were much tougher than us though, and they only barely survived.
2) I would argue that putting too much money in vanity space projects is actually more harmful. We would same more lives if we spent that money here to help educate people out of poverty so that they'd survive a calamity.
A Mars settlement is basically rich idiots (read Musk) trying to have a legacy while fear mongering common people.