I haven't played this one... but saturation-level advertising in ad-supported games might have played into the loop here. I play Endless Frontier, which is another related game that has (optional) "view an ad for a reward" mechanics, and said ad is almost always for Idle Heroes.
Insofar as Endless Frontier is pretty good about not forcing you to spend money, I've resisted trying another game which looks far more like whale-bait.