1) Yes he was the first to respond. One reason why he was the quickest to respond is that Allah knew (based on His infinite knowledge) that when tested in this world, the Prophet (s) would pass the trial the best and fastest. Allah has knowledge of that—that this person would make the best effort. So Allah honored him and gave him some sort of power or insight to say it the fastest.
2) The factor is free will. We have free will and we just use our free will the way we want. Free will is intrinsic to us, and philosophers state that which is intrinsic does not need an explanation for its cause. You can have two identical twins who grow up in an identical environment. One chooses good while the other chooses bad. They just use their free will differently.