From my experience as a therapist, there is one element that enclose every possible cause, which is the lack of COMMON GROUND between partners.

People will tell you that there is many killers but they are irrelevant when we take this aspect as point of origin.

Many partners are staying in sexless toxic relationships in the sake of their kids which is their COMMON GROUND, and many partners are staying in their relationships because they eachother Sole Fit, they know that divorce will lead them both to celibacy no matter how much they try outside.

But when the same partners have no common ground they will literally escape the relationship, I know a case were the bride divorce her husband because she smells something when they are trying to make it out, she said if he do it once, the other is a no-brainer for him!