On another note, how the fug did they even get the resources the build these things? Vault 13 alone cost $645 billion to build lmao. The amount of money Vault Tec spent on the Vaults proves how powerful them and the Enclave were.

The point of the vaults was to expose different populaces to different types of problems and events. If they put so much thought into this, Vault-Tec is almost definitely still around. Not in the corporate sense that you may think though. I would guess that there is a group of scientists somewhere looking over all the data and everything and monitoring the progress of vaults and such. Perhaps it was even scientists from Big MT. Or they could be residing in what used to be MIT. Either way, there still must be some way that even a few scientists are still around and keeping tabs on the vaults.

Seeing how high the gas prices were right before the Great War I think Vault-Tec was struggling to start their Vault Project on their own and then Enclave head honchos decided to just make it happen.
I'm sure they had enough strings to pull to just give Vault-Tec literally ALL resources they'd need. Humans included.