Even considering all those concerns the Mavs may have with him (which are pretty overblown for a 25yo 5x 1st Team All-NBAer who just took his team to the finals, and had already been to the western conference finals before that), it was still complete franchise malpractice to not at least shop him for a better deal.
The 'conspiracies' that the league wants a star in LA post-LeBron and that the Mavs owners are trying to move the team to Las Vegas make more sense than whatever the GM is trying to sell us, because they just straight up nuked their franchise—the front office comes off as incompetent, fans are pissed off and no player will want to go there after they intentionally just screwed one of the top 5 players in the world out of a super max deal.