Being good at something doesn't mean you'd be good at teaching others how to do it. In the last few years I've ended up with more clients who have come from other coaches, vs. people new to the process. Either there was a bad fit from a personality standpoint, or the coach didn't really provide a solid plan for that person's needs, mostly the latter.
I haven't seen a groundswell in folks coaching compared to the Carmichael days. I see a lot of folks utilizing online tools. Might be a local thing.
The USAC certification program is mostly test taking, having a shingle to impress people (and charge more), and providing a revenue stream for USAC, based on my experience.
Dunning-Kruger is strongest when someone has a credential. Not to say there aren't great Level 1 coaches, but knowing a theory and implementing one into a practical situation require different skills.