Why are girls like this in college?

I am in college and live in an apartment with three other guys and it is pretty wild. One of my roommates (lets call him Jim), is what some would call, a ladies man. There is no denying it. This kid juggles 4 -5 good looking girls at once. Now here is the problem. My other roommate and I have always been very perplexed by Jim's ability to lure women in. Jim is not in very good shape, he is short and has a tiny frame. However, all the girls claim he is "good looking". But, appearances don't matter, it is personality that counts, right? Wrong...Jim is honestly the most deceitful and manipulative kid I have ever known. When I first met him I noticed how easily he got people to adore him, even I thought he was awesome at first, but then I got to know him. See I am the kind of guy that reads straight through bullshit, it runs in my family. So I soon became the guy who would immediately call him out for every manipulative thing he tried to do, and I was commended for it. This created a tension between me and him. He knows that I wont tolerate his BS and for that he both hates and respects me. Anyway, back to the point. Jim is constantly nailing dozens of girls that clearly deserve better then him. I feel so bad for some of them because they think that he actually likes them when in reality they are just the flavor of the week. Jim had this beautiful, smart, caring, cool, down to earth girlfriend once and he cheated on her all the time! Literally this girl was amazing, but my buddies and I felt so bad for her. She clearly deserved better. BTW to clarify this has nothing to do with jealousy, which I know many people will be quick to point to. Neither me or my friends are unattractive or self conscious. We have all been in relationships. We have great personalities and are genuinely good people (unlike Jim). No, we aren't the most successful guys with women on campus, but we do alright. It just perplexes us why so many good girls are going after this guy, when they deserve better. Why oh Why? Please tell me what the deal is with these chicks? It is utterly unfathomable to me how the universe has allowed this to happen. Good people deserve better they are being subjected to here. This question would be easy to answer if this was high school, but its not its college! and we are seniors! I always thought girls were supposed to have matured by now. Thank you and sorry for the shotty explanation this is what I like to call a finals break.