I just replayed Fallout 3 and thought on how could the mutants organise that good. And when i got the idea that after things in vault 87 gone to hell the overseer used the results of their studies on FEV and turned into super mutant aswell. He became a super mutant like Fawkes and organized the Super Mutants as his own army.

What do you Think?

no

No, the FEV in the Vault made people into stupid mutants if they were lucky, the vault also had many failures. No one in there right mind would do that. Even still the mutants have a need to be around their vault that is why they are "organized."

Approach it as if they have the mind of animals(which at their level stupidity that's basically all they are), they band together only because of a common goal. Be it food or to make more super mutants. They attack in packs cause you have a better chance to score a kill and capture someone to turn them into Super Mutants. They would probably have a resemblance of a hierarchy with the stronger doing less work than the weaker ones. But their is no one leader/mastermind. You don't see one lion running the all the lions.

its only their primary purpose of survival, its either they smash their victims to pieces, or let it be like one of them. so super mutants are a group with a purpose, i cannot say that they are that organize, but overall they ahve a common goal. Its a wasteland out there.