The trend for Facebook has been going down since 2013. That maybe because people are using the app more than they are using it on a browser.

It might be indicative of something, but how many people are going to be searching for Facebook anymore? There's only so many markets to expand into, and if you have it installed you probably won't search for it much.

Not that I necessarily think Facebook is thriving right now, but I'm not convinced that Google Trends is a good indicator for established mainstream applications people already own.