Most probably, some contestants who ranked higher than you were caught cheating an removed from the contest and thus you ranked higher.
The question signifies your current rating is provisional. You read more about that here. In short, it means that your current rating may not be accurate because you have participated in only one contest. It might be your bad day, or a lucky day, or might be just an average day. The question mark will get removed when you have participated in 5 rated contests.