“Most of these are PC based, and there are currently no mobile games with large scale audiences yet.”

At 8:50 on a Friday night and 42,000 are watching Hearthstone on Twitch. That makes it the 3rd most popular game. It’s often the second most popular… apparently something super big in happening in CS:GO tonight. Nothing ever beats League of Legends on Twitch.

The main 2014 Hearthstone Tournament has a $250,000 prize pool. 2015 will have the same. In 2014 all Prize Pools combined offered about a $1mil. Some of the teams you mention competed last year and will be this year.

While the game certainly works on the PC, it’s also available for (and arguably optimized / intended for) both Apple and Android mobile devices.