
The fading of fad hit PlayerUnknown's Battlegrounds appears to be responsible for about half of the decline. Whether its its rise and "fall" hides continued steady growth elsewhere should become quickly apparent, as that game's player base reached equilibrium over the summer.
https://twitter.com/Steam_Spy/status/1024291642436734982
The anything-goes policy was seen as a capitulation to (or even an investment in) a rising tide of low-quality and often racist, sexist and plagiarized material. The emergence of financial scams posing as games is the sort of obvious result they were nonetheless unable to see coming.

