Women absolutely want the divorce more once they come to conclusion some aspect of relationship is over (typically the emotion part but simply spending less time together or feeling most of the burden of raising kids is enough).

Most guys can suck up now-loveless marriage trivially if kids are fine (after kids come, this is pretty standard path for marriages), heck we can still enjoy sex greatly in such situation. Most women, not so much. I know it sounds sexist, trust me I would be very happy if this wasnt true but when I look/ask/listen around it is.

As an cca older guy at certain age the patterns start emerging left and right, and my own marriage can see some of it, just like most other marriages around us.

Some make it, some don't. When it fails its mostly mixture of personality resilience of both sides rather than some objective measure of (lack of) quality of relationship. Its easy to judge but please be kind to those who are going/went through, they may have been a better partner than ie you and still it wasnt enough to sustain it.

They’re often sexless though.

Also it’s often fear of stepdads. My mom dumped my dad so she could date a string of abusive assholes. It would give me pause before leaving a marriage that wasn’t utter misery.