Many subject matters are initially so confusing and inaccessible that I have often wished for an audio-visual video lecture series in the following format:

Part 1: Music theory explained in just 5 minutes

Part 2: Music theory explained in just 20 minutes

Part 3: Music theory explained in 80 minutes

Etc. Starting with an extremely simplified overview and then making the overviews progressively more detailed.

Many people instead try to give simple explanations without making them short. But no confused beginner wants to be overwhelmed by a huge wall of text, let alone by a long theoretical book.

Unfortunately most people who have become knowledgeable about some subject matter then quickly and thoroughly forget how confusing, overwhelming or intimidating it was before.