I think there's more to it than simply winning a championship this season.
I mean sure, it looks great on the surface if they win a title, and it certainly gives him clearance from making what look to be the worst trade in modern NBA history, but there many other folds to this:
What free agents and lottery prospects in the future will want to go to Dallas given how Luka was disposed of? What happens next season when AD and Kyrie (if he stays) are another year older and unlikely to repeat? What happens 3-4 years from now when Luka is still in his prime and the Mavs (as they are now) have disbanded and they're back to rebuilding again, trying to find their next franchise centerpiece?
Financially and logistically, there really isn't a path for the Mavs to come out of this as winners, certainly not in the long run.