The difficulty is often due to professors (usually teaching assistants) who don't actually know the material and don't know how to teach. College is a night and day difference to taking instruction from someone who can actually do what they're teaching you.
I've been there. Studying more wasn't going to help. I saw students walk out of classes in frustration because they couldn't understand the foreign instructor who had poor command of the English language and didn't know the material anyway. From what I see with younger employees, it's gotten far, far worse.
Back then one might find a good tutor. Now, I recommend checking the web. For example, for car gear heads out there, here's a link to "Engineering Explained", a YouTube channel owned by Jason Fenske. He not only understands the material, he can teach it very well.
https://www.youtube.com/@EngineeringExplained/videos
I'd add that folks like Hickok45 and Paul Harrell can teach much better than most college instructors.
Calculus 1: Young kid only a couple years my senior (I had spent over four years Active Duty) stood at the board and taught only to two kids just out of high school who were very bright. He ignored the rest of us and actually would denigrate us for trying to ask questions.
Calculus 2: Some guy from India wearing shorts, a tank top, and flip flops. He stood at the board with his back to us and never turned around or entertained any questions.
Both times I dropped the class and went down to the local Community College (it was ranked as one of the top five in the nation) and took Calculus from a retired 70 year old lady with a PhD in Mathematics. She actually knew how to teach people and was my most memorable, in a good way, professor.