Mastercard is not going to drop Marriot because some manager got a little overzealous with his directive to make sure his franchise has good reviews.
You would be surprised. I've issued chargebacks before after offering every chance for an issue to be resolved with major firms (over the phone) and within 10 minutes of making a chargeback I got a call from the head office offering all sorts of things to remedy the issue. It doesn't take many chargebacks for a provider to can even very large accounts.
The payment processor can drop the client or increase the fees. MasterCard doesn't care that you are the Marriot if you have significant amount of frauds, significant meaning one percent or two.
True, but whoever handles the contract on Marriot's side is going to become extremely aware of a sudden spike in chargebacks and where they happened in short order.
It is possible, actually, if a certain percentage of their credit card charges result in chargebacks.