I am curious what were the expenses. Few things are as simple as they appear, but from the mobile games I have seen, they look like they could be put together by tiny development teams: simplistic (+recyclable) art and rules. Once the foundational app is created, feels like the further development could happen on a shoe string budget: artist to make new cosmetics and/or someone to develop additional puzzles. Presumably minimal server load from the whales to handle converting dollars into tokens.
I suppose the trick is in getting lucky with the one app that happens to hit it big due to some unknowable pattern of the universe. How many $0 flops preceded the blockbuster hit?