This was going to be my suggestion. Powerpoints really don't make sense outside of a presentation context. Writing an approximate script of the lecture will ai

This was going to be my suggestion. Powerpoints really don't make sense outside of a presentation context. Writing an approximate script of the lecture will aid in preparation, and then pairing it down into slides will help you find the beats you want to emphasize. At the end, you'll be left with an improved presentation, and good material to distribute to students who miss the presentation. The original presentation was in fact pretty comprehensible, but it was about presentations (and thus relied upon all the cheesy cliche accoutrement of presentation software), and done with the shortcomings of the medium in mind.