That appears to correlate strongly with the Christmas shopping season. For example, here's a couple similar looking trends for "ps4" and "xbox one": https://trends.google.com/trends/explore?q=ps4,xbox%20one

I don't think this indicates any lack of interest in the technology.

The problems with VR are much higher-level than anyone wants to admit. Nobody wants to wear a headset on their face. They'll try it for the novelty, but they have a hard time doing it very long, or mustering up the motivation to do it frequently.

VR won't hit critical mass until movie-style "holograms" are implemented (check out the video game in Her for an interesting example [0]), just as tablets didn't catch on until they looked and functioned just like the thin slates that had been dreamed of in sci-fi.

[0; NSFW] https://www.youtube.com/watch?v=r7MgbMI5zhw Example pulled from YouTube. Very NSFW language.

I'm waiting for 6DoF High-Def HDR Mobile VR.

And any AR headset that can pass the bar of "functional but also not looking weird"