I can't speak for anything that came later, but in the early videos the majority of the benefit was that the presentation was exceptionally clear, and focused on developing one little piece of a subject at a time, it gently paste format that you could easily pause and rewind over and over.

It was never about replacing exercises, it was there to help you do the exercises from your actual coursework, and to serve as a refresher reference for things you might have already studied but forgot some details about.

Also the videos usually consisted of a while of time spent physically writing out and talking through examples.