That's an interesting theory.
Like a lot of other things that are fun, MMA is legal on the reservation, and although it hasn't been mentioned publicly, I think the state may be trying to keep MMA on the reservations to distract the various Native American nations from the fact that the state is once again attempting to tax cigarettes, gas, etc. currently sold on reservation land.
The reading I've done has indicated that there's heavy opposition to MMA in many of the unions, and that seems to be a pretty big deal in New York.
The unions make up a huge portion of the special interests in New York politics, and while I can see pacifying the leaders on the reservation as a substantial motivator, satisfying one of the requests of a large special interest is definitely a big deal.