Nothing is wrong.

The risk profiles are different. That is only thing the payment processor cares about, same reason why adult services get shunned. Not because they are puritans, it is because of risk of frauds and chargebacks etc are much higher .

Coaching is a service unlike Tailwind the software that can varying success and satisfaction levels customers probably do higher chargebacks and stripe's automated systems or low level staff with a playbook likely rejected it until someone senior got to see the bad press and got it fixed.

Why would this be such a difficult thing to communicate to a customer?

"Hi, we've noticed an increase of frauds/chargebacks on your account so we have taken X action"

That also doesn't really explain why long-standing, established customer accounts were frozen with this particular business.