That is, I could trace back to the beginning of what they found confusing. I don't think I was special in having this ability -- it's just something people don't bother to do, or don't themselves possess the understanding to do, whether it's teaching physics or social skills (for which I have the same complaint as you).

This demonstrates a highly developed theory of mind. In order to do this one needs to both have a good command of material and a good understanding of what people are likely to understand or not understand. This is often very difficult.