Freshman year in college can be difficult, in many ways. It tends to reveal your weaknesses - academic, character flaws, talent limitations - that were masked within the friendly/cozy confines of high school. No longer do you have teachers who give you passing grades just to stay eligible for the track team. Now you're an anonymous student in big lecture halls where the professor or teaching assistant doesn't know or care about you. They quickly grade large numbers of midterm and final exams, with a good chunk not passing. If you aren't a strong enough student coming out of high school, freshman year will cut you down to size.
Some high school standouts last year have almost disappeared this year. They probably should've stayed away from college and found another way to train. Academic problems get in the way of athletic success.