NEW FRIENDS
Imagine the wife/husband suddenly has a crowd of new friends, none of whom please the other.
Maybe they are religious fanatics, drug users, licentious, dishonest, whatever.
Suddenly the home is a hang out with people all over the place so that the wife/husband feels a stranger in that venue.
As the friend maker has proceeded without the slightest respect to the other, as if s/he has no volition, it is not surprising when the other packs and goes.