There have been mass extinctions before, but it's a thing that happens once in awhile in geological time, so not really something to keep us up at night. Really human caused disasters - climate/pollution, nuclear weapons, rogue AI, are the things that are likely to get us.
If there are 5 companies, and 1 starts to do something wildly cheaper and better than the other 4, then we reallocate to that one and let the others die off (bankruptcy, acquisition, merging).
We like growth as a species because we always want more needs met at a lower cost. Then we can redirect the resources of less efficient firms to more productive ones. Onwards and forever.
We as civilization are not willing to prevent that event, nor able to fix/repair what it will do, so what makes you think that we might be able to do anything with faster events like a supervolcano eruption or a big enough asteroid impact?
off the top of my head, given unlimited budget, I'd probably have a massive vault of seeds (not just in variety, in quantity, too,) and adequate staff in rotations in a deep-sea bunker. not near a fault line, but deep enough that surface conditions are less likely to impact (no pun intended). Sea vs land because "digging your way out" become less of a problem. If you had a truly unlimited budget, one could imagine an Ark of embryos and a sufficient population of young does of each animal species you sought to preserve.
Though not a deep sea bunker. I imagine there would be trade-offs to that too, like water leaking. Plus, access without submarines could be difficult.
