The mutants on the west coast are mostly remnants of the Master's army. While a great many of them are prone to violence and have more teeth than brain cells, there are far more "civilized" ones than those that came from Vault 87 on the East coast, which seem to have been created by other mutants, rather than an outside party like the Master.
The ones in 87 were trying to create an army, while Master was trying to create a new race that would become the new world order, so to speak.
The only civilized super mutants I can think of on the east coast would be Harold, Uncle Leo, and Fawkes, while in the mojave, there's ones like Keene, Marcus, Neil, Tabitha, Lily, Mean Sonofabish, all of the ones in Jacobstown, and so on. Sure, a lot of them are bonkers, but they're still somewhat intelligent.
"They asked me how well I understood theoretical physics. I said I had a theoretical degree in physics. They said welcome aboard."