I think fangirlism highlights one or a few of the main differences between men and women's sexual psychology. If girls find status attractive, and if girls tend to find men attractive in part because other women find them attractive, then we would expect celebrities to be generally more attractive to women in the absence of competing factors in men.
I, and most of my friends have not had a crush on a celebrity since we were about 14, so maybe it's an emotional immaturity thing.
tfw Victoria Coren isn't my waifu
Wentworth Miller is too hard to resist falling for
It is due to hypergamy as pointed out previously.
Men pretty much are attracted by looks, women are attracted to looks, money and status. Now a guy can go to a bar and there will be women equally as good looking as say Jennifer Lawrence...Now a women can find a guy of equal looks of a famous person but they will never have the money and status of say a movie star or rock star...this is why women have celebrity crushes.