> [...], but what I (and I suspect GP) might want, is to know why a few of the key steps might work.

It's been some time since I've used the step-by-step explainer, and it was for calculus or intro physics problems at best, but IIRC the pro subscription will at least mention the method used to solve each step and link to reference materials (e.g., a clickable tag labeled "integration by parts"). Doesn't exactly explain why but does provide useful keywords in a sequence that can be used to derive the why.