Not my experience at university (maths degree). The people who were very good also put in a lot of time. But not in a forced way, they simply enjoyed the subjec

Not my experience at university (maths degree). The people who were very good also put in a lot of time. But not in a forced way, they simply enjoyed the subject so much. It's possible the people you saw had already mastered the subject even before you took the lecture. Or it had so much similarity to something else they had already mastered that it became easy for them.