Cause they’re nuts.
Yeah, because starting to spend every day of your life with the type of person who is by nature effectively your complete opposite and comes from a completely unknown background, family, city, community etc. makes perfect “logical” sense.
I’m all for marriage, and would say such a person is wrong in approach generally speaking.
But to call a person nuts? No, that person is probably using their seichel just fine. 🙂