Seriously. It's not some big secret that the Adelson family wants to get gambling legalized in Texas. https://www.espn.com/nba/story/_/id/39012772/mark-cuban-mavericks-adelsons-sports-betting-texas https://www.nbcdfw.com/news/busines...andmark-destination-resort-in-dallas/3946186/ Purchasing the Mavs is just a small part of their plan in their push to get gambling legalized. Moving the Mavs away to Vegas would be counterintuitive to their plans and would kill any chance of ever being able to build a casino in Dallas.
100% The NBA would never allow the Mavs to leave Dallas. That is the end of the story. Plus, Vegas will be an expansion team whose new owners will pay a multi-billion dollar expansion fee.