Why do boys like mean girls???

There’s this boy that I thought liked me. Because he always sent me hearts, called me cute, put his hand on my knee in class, etc. so NATURALLY i thought he liked me. last week, my friend made fun of his pimples literally out of nowhere for no reason, and he got mad and made fun of her back. then the weekend passed and today (monday) he asked her out!! instead of being polite or anything she sent him a selfie of her doing a thumbs down with the caption DENIED and then laughed about it with our other friend in class right in front of him!!! i just don’t get why he’d like her?? she’s so mean to him!