Not every trait gained by evolution directly affects the likelihood of procreation.

Just wanna interject to the opposite, that every trait gained by evolution directly affects the likelihood of procreation.

I'm just speculating here (and a lot of evolutionary theory is), but the husband who has wife goggles may have children and grandchildren who have better chances of surviving and passing on their genes. So a husband who sticks by his old menopausal wife might mean the old lady would be a better grandmother. She might be more willing to take care of her grandchildren, giving more time for her grandchildren's parents to forage and hunt (or in the case of modern humans, work full time jobs without needing to pay for daycare). This means better chances of survival for the next generation.

A husband how disposes of her menopausal wife to get another wife (or two) means the husband now has to share the gazelle or bison hunted and killed with many a children from 3 or more wives. The protein intake of this big brood will be considerably less per child, compared to a husband who stuck with just one wife and say 2 or 3 children. So the single wife husband has more chances of having children that are stronger through better nutrition, thus raising the likelihood of them passing their genes.

Speaking of genes, the monogamous/wife-goggle husband may have selected for gene/DNA/chromosome sequences that affect the oxytoxin level years into his multi-decade marriage. His oxytoxin may be more long lasting for decades. His love/oxytoxin "loading" gets passed on to his brood and that wife-goggles gene/DNA/chromosome sequence may in fact be passed on to his grand children.

Compare this to a man who's oxytoxin loading gene sequence is short. Maybe his oxytoxin loading falls immediately a few years into marriage, so he gets another wife, and another, and another and after a decade or two he may have 4 wives and 20 children, all competing for his sole protein provision with meat hunting. Maybe all the children became malnourished and a quick famine could easily have wiped this man's whole brood, thereby killing his short oxytoxin chromosome sequence for all eternity.