Khan did not throw at you a 100-slide Powerpoint deck in 45'.

He really took the time to replicate the manual teaching process of writing on whiteboard. He improved upon it by using colors. But basically had the same pace as a teacher writing on a whiteboard.

When professors are given a projector, they just throw together some slides and add their narration.

This is not very efficient. To learn you need to suffer. Or you need to watch the suffering.