It does seem like a good indicator for games that are receiving active development and I'm not suggesting you're wrong. I would point out, however, that those of us in PF1 games cannot buy new PF1 products from Paizo because they aren't being made. One local DM kept his subscription to Paizo adventures but plans to convert anything he likes to PF1.That PF2 keeps climbing and it remains number 2 on the sales chart seems to be an indicator that it's steadily climbing.
EDIT: I am kind of interested to see what happens with Hero Lab Online and their effort to expand it to cover PF1. As I understand it, there will be a small fee to extend any sources you already own in the OS-native version to the online version. There's some debate in our player bases as to if it is worth converting to the online version or just sticking with the OS-native software. Not everyone is interested in the online version. Some are really into the online version. Others are weighing the relative merits (access) to the demerits (continuing costs).