You are assuming that evolution is reasonable and would make good genes dominant. Evolution is more about luck and not being critically unfit to live, thoughEven taking that into consideration, if the Chad Heroes are actually Chads, wouldnt their genes be like 99% dominant ones? this is the reason why the survival of the fittest can even happen, what HELPS the lineage whit defeating Demons? being 6'5 genetically gifted into being ripped as hell and having T levels over 9000? or having a big ass, low T levels and lack of hormonal balance?
What HELPS defeating Demons is having Goddess' blessing, and that's about it. Hyperspecializing into it would make everything BUT the sperm quantity (for securing a heir) and being submissive to Goddess (to maintain the blessing) redundant. Apart from those two traits there's no other functions to heroes, is there? They don't need strong bodies to kill demonds, they don't need any beauty or talking skill or anything to bed women, they are just... eh??? Being a Chad, so that Goddess notices them, basically cursed first heroes' lineage into getting Cucked down the line