IMO natural intelligence, work ethic, organization/time management, interest in what you are studying and even a bit of luck (getting the right professors etc.) all contribute to the success of those that are 4.0 students in college. I knew a Physics major in college and he just got it. Homework that other students would spend hours on he would have done in an hour. He was organized and prioritized his time well. He never seemed to be working hard but was always prepared. He had a social life and seemed to enjoy himself. I’m sure being “smart” was a large part of it but I’ve known some smart people that were always behind figuring they could “catch up”. Usually that didn’t work out for them.