Yesterday we was to my niece's wedding party and all the girls were crazy for one of the waiters. And I myself have to agree that he was a very good looking guy.
Consider "crazy for" to mean "very enthusiastic about". We often say that people are "crazy" or "mad" about, or for, something or someone. Figuratively a comparison is being made, perhaps, with obsessive mental illness, although 'crazy about/for' used this way does not imply any abnormality.
2 Extremely enthusiastic.
‘I'm crazy about Cindy’