We have amazing coaches, and all of the team coaches (and at least most of the rec coaches) have a gymnastics background. In fact, all of the team coaches have an elite and/or college gym background. One has worked with Olympians. There is no cheer program at our gym, though I know there are cheerleaders who take the rec tumbling classes. I actually have no idea where the HC found so many talented coaches, since we live in a pretty small town, and I think only one relocated to work there. It seems like there was some sort of Field of Dreams "If you build it, they will come" magic going on.
I would not like it if former cheerleaders were coaching team at all, though I would think it would be fine at the preschool level where it's mostly all about moving your body and having fun. And even other "rec" classes as long as they had someone mentoring them on stuff like emphasizing proper form, etc. It sounds like, from what I've read here, cheer tumbling is a different animal, so maybe any tumbling above and beyond cartwheels and rolls might be better left to the gymnasts. You definitely don't want them building any bad habits that the kids will have to break if they stick with the sport and move up to team.