Earlier quoted context omitted.
What would have to happen to earth to make it less viable a place to live than mars? An asteroid rendering earth’s surface uninhabitable? Even that wouldn’t be enough - there’s still so much more on earth to sustain human life than any planet in our solar system. Apart from proof of concept I just don’t see any practical reason to colonise mars.
I don't get your point. Having a self-sustaining colony on Mars ready when suddenly the brother of the Chicxulub impactor appears on the radar and will hit in less time than it would require to create massive underground cave systems utilizing geothermal power would take to build, will literally save the species. And that is just one apocalypse variant. Nuclear holocaust. Antimatter bombs. Possibly even a massive gam…
Elon often talks about how exploration is exciting and inspirational and a prerequisite for future interstellar travel, and that works better as a justification to go to Mars, IMO. Also, while those disasters might not completely wipe out humans on Earth, they could reverse centuries or millennia of progress and delay further space exploration for hundreds or thousands of years if we don't do it now while we have the chance.