I think its retarded that some female porn stars are married

For some people porn is just a job. If you have your spouse's permission then it's not cheating. They go to work and have sex for pay. When they go home they have sex for love. They are able to keep the two lives separate.

Do you actually think what you see in a porn video is fun sex?
"Cut" yells the director. In rush the make up people and the fluffer, some set guys and the lighting guys surround you.
"Clear set, ready to roll." and you're alone with the other actor(s) again, "Action" and you go back to doing whatever you were doing before.
It's a job and a pretty tedious and boring one, unless you are like 12 years old and think she's yelling in orgasm, instead of acting.
So why not be married?

And what do the wives of married male porn stars think about that?

Same reason why some male pornstars are married. They've got an extremely open and trusting relationship.

Take off your fedora, I think it's causing brain swelling.

It's comical, really.

It's acting. And they probably let their men fuck around too in return.