It is completely normal to wonder why this happened to you. Sexual assault happens to boys, girls, men and women of all ages, races and cultural backgrounds. Sexual assault does not happen because of what someone wears or does. It doesn't happen because someone is rich or poor, young or old, popular or not. It does not happen because of where they were. The offender may be someone the person knew, even someone they trusted. The offender may have been a complete stranger.
A sexual assault happens when an offender chooses to assault someone anyone.
So, if a sexual assault has happened to you, you are not to blame.