system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout] Where the hell does Vault-Tec get all their employees, that they are almost all willing to do such horrible shit, even despite the likelihood that they would be horribly murdered?

So, from all the games so far, almost all Vault-Tec employees are complete moral monsters, with them willing to do pathological experiments and what not.

That the Overseer of Vault 81 is the exception rather than the norm is telling.

Was there a sale?
gpt
The majority of Vaul-Tec employees were actually normal office workers, sales representatives, construction workers, and other relatively normal people who were completely ignorant of the true nature of the vaults. A few office drones got wary every so often, but they were quickly silenced. 

But when you get into actual vault staff and higher ups, there can be a few explanations:

1) They firmly believed that they were doing the right thing. The world was heading toward destruction no matter what happened, so preserving the species was a top priority. The suffering of a few hundred souls was nothing compared to staving off extinction. Plus, it usually wasn't them who were suffering directly, so they could disassociate from the dilemma. (Leah Remini did a very interesting take on this mindset when talking to Joe Rogan recently. It's very frightening and incredibly powerful, and Vault-Tec would have it in spades.) 

2) The pay was EXCEPTIONAL. Vault-Tec rarely spared any expenses, except when intentionally, and paid for top of the line facilities and staff. When people get enough compensation, they can do some terrible things. 

3) They had no choice. Perhaps some employees had no other career alternatives, or the company had blackmail material on them. The world in 2077 was just as bad as 2287, just in slightly different ways. There were undoubtedly cases of employees forced into doing terrible things or face starvation/their family dying.

4) Us-versus-them. Employees of Vault-Tec were indoctrinated into thinking they were part of a special club, a group of people who were better informed, better prepared, and better motivated to save the world compared to the average American. This kind of separation made the employees form a kind of tribal bond with each other, and mentally separate themselves from the common folk, to the point where they barely saw the other citizens as human beings. Of course, in situations where shit really went down, like in Vault 111, that tribalism was as fragile as it was horrifying. 

5) As you noted, not all of the overseers and employees were part of the program. No two human beings are the same, and some have the power to look past indoctrination/pay/brainwashing to see the bigger picture. And some, like Doctor Braun, were total monsters who just happened to have unique technical expertise. But the company kept them around so they could use their gifts in other applications.