What's with the discrepancy?

So I started playing on Chess.com (regularly) almost exactly a year ago. I've made a lot of progress from around 300 blitz rating, and other than some recent losses (too much of the 🍻) I've been hovering around 1200. 

Facebook has a chess game via Messenger, and i started playing recently, and have quickly moved up to 1800 within the past 3-4 days. I play blitz, which is 1 minute per move. Games last quite awhile. As long, if not longer than 5|5. 

I've noticed that players are just not as good as here on Chess.com. At least that's what I thought when I hit the 1500 mark. Now, at 1800+, I find it hard to believe with a 600 point discrepancy between Facebook's app and my Chess.com rating, that the players on Facebook are that much worse. 

I'm starting to wonder just how common cheating is on Chess.com.  Or if there is another reason for this discrepancy.

Any ideas would be much appreciated.

Regards

I don't think I have ever seen any statistics on Facebook messenger chess, so we can't do a comparison.

One minute per move is equivalent to 60  minute games here. Those are rapid, not blitz. Ratings here diverge by hundreds of points between those for rapid and those for blitz.

Okay, yeah that makes sense. It's interesting to me nevertheless. Frustrating really...

There's gotta be a reason ya know...

But thanks for your response!