My small city of around 200K just had one big wireless player (who also happened to be the cable company) announce they are leaving the market (and selling the spectrum licenses to one of the big guys) and the other three I know of buy their bandwidth from.. well, that same cable company and/or the local telephone company. There's no other place to ultimately buy bandwidth: there are three companies that transport and transit: the big regional telephone company, the local cable company, and Facebook. Everybody else is buying and selling Internet from the big guys.
I can't talk about the health of the small wireless ISPs here, but if you sit down and do the math, they are likely just barely making a profit. This may be why the local cable company has exited the wireless ISP market. (I live in an area with a small urban center surrounded by miles of farms and ranches, the cable company's strategy was to use the wireless to extend their range to these rural subscribers and infill in the few areas their cable network didn't cover). And this small cable company had the first LTE network on in the state, so they had a hell of a head start.
That's pretty much the picture in most places: the little guys are very little and increasingly getting smaller, and the big guys are only getting bigger.