He's basically just another doomsday cultist.
Pretty much by definition the first people to prepare for any disaster will be people who are or at least appear to be unreasonable.
We benefit from a diversity of opinions, even when some of the opinions are wrong.
https://dustoffthebible.com/Blog-archive/2012/05/25/the-end-...
And if you're going to pick a date, why one over another?
+7 years seems a reasonable goal to make progress towards
Also it's effin goofy. Nerd CEOs building their underground fantasy post apocalypse shelter, thinking that not only that the society will collapse I their life time into a Fallout-ish World, but that their shelter is going to be of big help. But the goofyness is just that, it's the promotion and prophecies that are harmful.
The number of people and amount of treasure spent on it is a rounding error.
Let other people have their hobbies.
Thiel is rich and powerful, but he isn't that rich and powerful. There are more than enough counterbalancing forces.
And it starts to be way too thought policy (for me) deciding "You can't be rich and worry about civilization collapsing."