As usual late to the party. My own $0.03:
1. First of all divorce has become more acceptable so people are not as reluctant to end a bad marriage.
2. I wonder (but have no real evidence to prove it) if kids who change their levels of frumkeit post HS and then change back to where they were has anything to do with it?
3. IMVHO - I think that it's the result of shidduch mishegoss gone to far.
#1 is pretty straightforward, please let me elaborate on #2 and #3:
#2 - imagine this, a young MO boy goes to Yeshiva in Israel, and as a result, he becomes much more religious. Instead of going to college, he spends a few more years in Yeshiva. They find him a shidduch. He gets married and starts a family. But after a few years he grows disdainful of the community he's in. He decides that he doesn't want this particular lifestyle anymore - he still wants to be frum, just go back to his modern roots. (Again, I have no evidence to prove it, short of one or two friends that this happened to - essentially they wanted a different level of frumkeit than their spouse)
#3 - Take what I say with a grain of salt because I don't live in the shidduch world. But from the few friends I have that are within it, I hear that people are so concerned they leave out things that should probably be raised BEFORE you get married. Some examples of stories that I heard:
- A young woman who got divorced from her husband after discovered that he had been hiding that he was taking drugs for a psychotic condition
- A teenager who had a certain medical condition that was manageable by drugs, but better resolved with a surgical procedure. When his parents were told by a doctor that he should have the procedure they refused to do it because they were worried it would mess up both his and his siblings shidduch chances when word got out that he did it.
I realize that there are two isolated incidents, but I can only imagine they come from a place of fear. I also imagine that there is a chain effect that impacts a 'p'gam' on the whole family if one of them has some sort of 'psul' vis-a-vis the shidduch world. Given that, it's also possible, that due to some familial pressure. Someone might endure a bad marriage for a few years until their youngest sibling gets married off so that their divorce won't impact their little brother or sisters shidduch chances.