Actually it makes perfect sense. It makes more sense for a woman to cheat than a man.
It's unscrupulous and I don't condone it but whatever makes a wife faithful, it's not because her biology is standing in the way. In fact thanks to hormones, during each cycle a woman is attracted to different things and different types of men.
If we are to simplify people and take them as one dimensional then as per biology women should marry the man who is most able to provide and if he is also the best genetic option then only have his kids but because of her biology she's attracted to two different types of men each month. So stay married to him and mix your genes with him, cheat with the other type (maybe the softer emotions, romantic type) for her other needs.
If it's the reverse and her husband is able to provide financially but not the strongest genetic option then biology would still suggest that she mix her genes with the superior mate so have the side pieces kids but live off of the better off husband.
She is the one who would carry the baby so unlike a cheating man who has to slip a woman the plan B, the cheating wife knows her cycle, has the option to take precaution and remediate any mistakes. A cheating wife who is unscrupulous and careful enough can have her cake (well off husband) and optional extras (side piece(s) to meet unmet biological drivers).
But cheating and sleeping with more than one person are not the same thing. Just because you have sex with other people doesn't mean you have to lie about it aka cheat. But the consequences of being honest about sleeping with other people outside of marriage are potentially more disastrous for the female...An unfaithful woman who wants her children to be provided for will lie so the husband doesn't doubt if they're his aka biology.