People can change over time in ways you wouldn't anticipate, but if you marry someone only once you know them deeply (and if you don't, you deserve what you get), you should be reasonably confident of what sort of person they are or could become.
"Reasonably confident" is a remarkably weak threshold for putting half of one's future wealth on the line. What else does one deserve to get, as "punishment" for not being sufficiently perceptive of a future spouse's character?
Half of your wealth is very very small compared to losing custody of your kids. If she leaves, the legal system will almost always make sure she gets the kids. Unless you have kids, it's difficult to understand how horrible this is for dads.
Smart people aren't universally smart. They're smart at the things that they choose to be smart at. I know a few brilliant people that are geniuses at their chosen field and yet wouldn't notice if their spouse went off to Vegas without them.