I've always wondered what the smart, funny, and together Irene of the film saw in the goofy and socially awkward Cornelius. I would have guessed that she could do much better, even if the only men she meets are salesmen who come into the shop to sell her things. Crawford really takes a role that should be charming and sweet, if somewhat awkward with women and goes over the top to the extreme. It can be funny, but he mostly leaves "charming" at the door. I assume this is what Gene Kelly wanted and he was directed to play the role in this way. I wonder if Crawford's interpretation would have worked better on stage where he would have been playing to the balcony.
Even Streisand, in the hat shop scene, seems to try to get Crawford to reel it in, in the guise of her character mentoring his in dancing.