We’ll have reduced the chance of something wiping out everything we hold dear by a factor of two.
Be honest. Trying to exclude the basic animal instinct of survival, who will you hold dear that will be affected by any of that? Sure, we can predict cosmic catastrophic events, but we still can’t stop them. And looking at a perspective that capitalists ((at least in the most recent history (current affairs)) have been the most interested in finding something off the planet and trying to figure out Mars.
Now, I also consider that going to Mars would be a long process. I bet my life that the first few crews that head toward Mars will either die or never be heard from again. There might be that one or two Wayland’s, but the vast majority of people who can afford to leave the planet won’t do so until they can be guaranteed a high chance of survival. Meaning that they’ll let a multitude of people die before they’ll allow themselves to be hurried off to a brand new start. You should know as well as I do that those billionaires aren’t going to save the masses. So even if sustainable existence occurs in our lifetime, are you sure the people you hold dear are going to be saved? And what right do we have to overpopulate another planet?
Huh? Sure we can prevent some cosmic events (asteroid redirect) and even mitigate others, by having backup of life elsewhere in the solar system. We have the technology, would you rather everything dies because of some ideal? Don’t let perfect be the enemy of the good.
As to your last points, that’s how it’s been done during the last few expansions. But spaceships are expensive - tonnage to mars is insanely expensive. The incentive is to get a return on your investment: a sustainable colony. Sure, the billionaires won’t be the first, but someone has to be. And what right do we have? It’s our imperative to ensure the continuation of life by spreading it through the cosmos. Anything less would betray our base genetic instincts.