Do you mean the husband's skirt chasing, or the two leads? Not gone hold you, I have never cared about women cheating on their husband's with other women in historical settings - for multiple reasons, it was lowkey the default if they wanted to be with someone they actually loved.
in general, just the entire appeal that some people have to chase after people's who are already in a relationship;
if we are talking strictly about this manhua, i can't take the historical settings argument because it is way too tricky, as in there's way too many variables such as society, local culture, era, individuals etc
no matter what the justification is, i just think going after someone who isn't single is just wrong, get both single first and then i will be content