It's interesting to look at those games from a business/economic perspective.
Imagine you create a mobile game called "Data Entry Crush" where the game would send players an image of a document and they would carefully type in the text for it. You give the game to players for free. On the backend, you sell this as a service to companies needing data entry where they pay you to turn their images into text.
In other words, like Mechanical Turk, without paying the Turks.
Of course, this would never fly because people don't find data entry very fun and it's pretty obvious to them that they are being had. They know they are providing something of value to you and won't do it for free.
What Candy Crush and friends did was find an exploitable loophole in human pyschology. It's hard to get people to do something that clearly looks like valuable work for free. But it turns out people aren't good at realizing their own attention itself has value. So what do you do? Make a game that's a little fun to play to keep people going, and then pepper it with ads. Those ads take some of the player's attention but since humans seem to undervalue that resource, the players allow it to happen without getting irate or expecting compensation.
And then, as before, you make all your money on the back end. You let companies pay you to put those ads in front of people. It's like an arbitrage opportunity where human attention is more valuable to (A) companies than it is to (B) the individuals who have it, so you take it from B, sell it to A, and keep the profit.