I doubt that's the case. The more likely cause is that after six months of being on the market people have realized that the game just isn't any good. Paizo's foray into Pathfinder began when WotC released 4e and people wanted an alternative to a watered down version of what was once a fun game. They established an entire market based on this, and then turned around and released a second edition which is a watered down version of what was once a fun game. If people want that why would they need to go to a secondary market when there's already a primary market of the exact same thing currently having a resurgence (D&D 5e)?
Honestly, the only thing that doesn't make sense in what little of the sales statistics we can see is why there was a spike in sales over a month ago (early tax returns maybe?). Everything else has been exactly as expected since the beta was made available for public consumption.