You might be right that he was just overwhelmed, but if I were in his shoes, I feel like my first thought would be "Oh no! How many dudes did my wife bang and how much therapy will I need to get over it?" There's no humans there, either, so that means she had freaky alien sex LOL. Figures Mark is from the one alien race that doesn't appear to have bigger dongs than humans, so whatever good lovin' the aliens are giving her is something probably more than Mark can offer. I'm guessing they will go for a parallel to when a guy finds out his girl slept with a black dude and they get self conscious that the black guy likely had a bigger cock than theirs. Mark will be freaking out wondering what kinky stuff those aliens did to his wife and jealously wondering how to live up to it.