To be crazy about someone or doing something is an expression which means to be very, very, very keen on something or someone, or to be fond of something or someone. We also use the expression to be nuts about doing something.
For example, some people are crazy about cooking, ( I know, how is that possible?!) and others are nuts about climbing big rocks. However, at the moment, for me, I’m crazy about playing squash even though every week I lose and get my ass kicked. In addition, I’m crazy about my thermal underwear because I’m soooooooooooooooooooo cold!