I see this in the older chevra. I don’t think it has to do with intelligence; B”H we are blessed with Intelligent boys, too. But when they are younger , everyone is at the beginning of everything, and when two people are zoche to get married, their married life takes a piece of everything. If he’s going to be a high powered lawyer, she’s already pregnant and is thinking about the kids and wnats to stay home. If he’s in Kollel, her priority is top dollar now, with being able to balance time with the kids. Being a Doctor/Lawyer for a girl, usually won’t cut it.
BUT if things take a while to develop – well, boys usually rot without wives, and girls thrive without husbands. So you the longer you get down the shidduch pole, usually, she’s beautiful, accomplished with a checkbook and a nuclear physicist – and he’s – be it working or learning, degree or not – still kind of wandering around, working in his uncle’s store/law firm. Usually, guys do not have the same degreee of success in their years. Girls have a blast. So the gap gets bigger and bigger, and how on earth is she suppose to look up to him? Obviously, this doesn’t apply to all guys, but I think it’s a pretty good rule of thumb.