[CamperBob2]

Exactly. If the teachings in the patent aren't necessary or even useful to future developers, then what was the point of granting a 20-year monopoly in the first place? No research expenses needed to be recouped, and there was never any danger that some arcane knowledge would be locked away forever as a trade secret.

Many patents don't reward the first person who solves a given problem, so much as they reward the first person to encounter a given problem. That person adopts a trivial, obvious solution and the USPTO cheerfully rubber-stamps it at everyone else's expense. This was clearly one of those patents. It cost Amazon essentially nothing to research, nothing to develop, and nothing to implement, but the rewards were immense.