It could be that my professors were simply not that good, so that I don't really understand this. I mostly groked the subjects by working through the books and exercises in them. The professors' lectures almost always went over some detail too quickly, so in a 3 hour lecture, I usually ended up following only the first hour or so.
My question is maybe better put as: what quality or approach makes them great lecturers?
Having a class in databases from the person who was the DeWitt Clause in Oracle licenses.
I had his class before (the aforementioned sophomore data structures and algorithms) and I knew he was a good lecturer. That wasn't a question. It was a "too much going on that semester and I wasn't able to do the assignments in a timely manner".
Professor Landweber's class had a waiting list that I scoffed at as a college student and looked for something that I could get into and fill the requirement without realizing who he was. It wasn't until later while reading the UNIX and Linux System Administration Handbook and seeing an image in there that was attributed to him that the name clicked but he wasn't teaching that next semester and I had filled that requirement elseclass.
Another regret was dropping numerical methods with Professor de Boor ( https://en.wikipedia.org/wiki/Carl_R._de_Boor ) when I couldn't get my head around splines rather than going to his office hours (he was also the undergraduate advisor and very helpful).
Those classes could have changed the trajectory of my career. I was looking at being a sysadmin instead and writing perl and keeping some big iron running. My career pivoted from sysadmin to webmaster to web developer (perl) to web developer (Java). I have no regrets from that path - I do have regret for not learning what I could from the experts in their field when I was in a place and time to learn from them.
It could be that my professors were simply not that good, so that I don't really understand this. I mostly groked the subjects by working through the books and exercises in them. The professors' lectures almost always went over some detail too quickly, so in a 3 hour lecture, I usually ended up following only the first hour or so.
My question is maybe better put as: what quality or approach makes them great lecturers?