facebook killed "social gaming." social games became large because fb encouraged spamming invites to get more people to use and grow facebook, and then slowly locked down that channel. So, you could spend $5 in ads to get one user, that user would get 5 friends to join, so it only cost $1/player, and theyd spend $2 on average. This was great for building the platform, but once at critical mass fb needed to capture that money so they squashed the social channels in favor of their ads.

So now what happened is gamers on fb only would spend say $2, without invite spamming at $5 installs you lost money. But turns out people who own iphones spend money more easily. So everyone moved into mobile. While it didnt have the social channels, you could extract say $6 per user, so that $5 per install was still profitable. Before Apple really cracked down on some shady companies(they bot you into the top 10, you get thousands of installs from top 10 placement), you could drive that cost down even further.

Today, all the free to play apps in the app store follow a lot of the same patterns as social games - clash of clans is just a clone of backyard monsters(fb), which was probably a clone of something else. Some have social elements, mostly top charts, but... These games were never truly social, they were just addiction feeding machines. Effectively they just changed the name to f2p on mobile.