I think one of the BIGGEST problems is, simply, that people are not really honest with each other before they get married.
Possibly not honest about many issues, but most importantly about what their own true hashkafas ARE. What they really ARE, not what they are SUPPOSED to be, or SHOULD be, what they ARE.
They “fake” their hashkafas (maybe even to themselves) to be what they think are what people want to hear.
Why? Because they want to GET married.
They don’t stop to think what the ramifications of this deception will be when they ARE married.
BIG, BIG, BIG mistake.