Warning: This is me as a fellow GM talking, not me as a commissioner.
The only comment I will make on this that I have made a deal with one of the teams, there is currently a trade in the queue for after the season involving one of the teams, and there are more examples of the new GM's making other trades. ALL without Jazz.
Fact check before you make large stupid accusations. Literally none of your points hold ground.
Sharing an IP address: IRL friends see each other in person, I'm not sure if you understand how that works. Inviting a friend to a league and showing them how to make an account is pretty standard.
Them never posting: Do you seriously think Jazz would take the time to switch between five accounts (by your definition in your post) to make deals, send messages, and also be dumb enough not to make a post here or there?
The new GM's don't make any trades without Jazz: See above + I can only imagine what it is like to run Jazz's inbox. Without a doubt in my mind he is the most active GM in this league, constantly sending out feelers and trying to make deals. Jazz has made 30 (THIRTY) deals this season, want to know what 2nd place is at? 16. It's not a surprise to me that he will make deals with the new GMs, with whom he is also friends with.
Those are your only 3 points you make in your post for this massive display of a formless accusation.