The weighting of college admissions exams (which are heavily weighted toward measuring ability rather than study skills) and high school grades (which measure a combination of study skills and ability, such that you can't pull the two apart distinctly) in admissions means its easier for someone with high intelligence and weak study skills to get themselves in over their head in the college program they are admitted to than for someone with less intelligence and stronger study skills to do.
Plus, the difference between not having study skills and needing to learn them from scratch and having study skills but needing to study more is one of kind, not merely of degree.
(But, sure, lots of people have transition problems with college, even though those problems can have different sources, natures, and manifestations.)
Studying is more of a practice/habit, than an area of knowledge; someone that has avoided needing it because they pick up knowledge well without it and hasn't had their ability to pick up knowledge challenged isn't necessarily going to pick it up easily, especially, if they have many years of strongly ingrained contrary habits when, suddenly, for the first time their ability to gain knowledge is stressed and they need studying to keep up.
Sure, its not an impossible skill to develop. OTOH, when you've missed out on many years of before-college skill development in it and try to catch that all up in time to make a difference once you get to college, its not all that likely to succeed as well as you'd like.