This is a good discussion to have over beers, if I am ever in your city. But in short (or not so short) I think there is money in making free 2d mobile games, but not so much in selling 2d tool to make games. Big game developers already have the engine they are using (sometimes in house or sometimes one of the ones available in the market) and small and Indy developers want to use something free and if they win the lottery (have a hit game) they’ll pay someday. Many business try to keep core to their business. So if they make games they probably have a focus on making games. Not servers and definitely not maintaining a 2d tool.
A small AdNetwork that is trying to sell ads and doesn’t have that much inventory might see a 2d tool with some established users as a way to get inventory they can buy cheaper than in the open market and sell for a profit in that market. Make it as convoluted as possible to use anything but their network and you’ll get a portion of the user’s inventory. I think that is what attracted Fuse and Appodeal. I don’t know how many impressions the collective of corona has but just looking at my numbers, I suspect it is in the hundred of millions a day (maybe more).