It helps, but it's certainly not the dominant effect. I don't know anyone who went to an elite university without significant baseline intelligence. I've seen so many students who still didn't do that well even after extensive, expensive tutoring.
For example, SAT coaching only increases scores by around 50 points. [0]
For example, SAT coaching only increases scores by around 50 points. [0]
[0] https://www.jefftk.com/p/sat-coaching-what-effect-size