Las Vegas is a growing city. Currently #29 from #63 in 1990. On top of that, they probably get another 1M tourist a week. NFL game will draw them as well. So right now, it's the bigger, better, and growing market.
Oakland is going the other way. Currently #35 down from #25 in 1990.
Now throw in free 2.5B, what's so surprising? Any owner would be stupid not to take that deal. LV is desperate for some pro teams. It's #29 US market, and millions of tourist each week. I don't think they'll have problems filling the stadium nor building a fan base. LV is not too far from LA/OAK that it might still stay the favorite team for those locations. Who else will OAK root for? SF?
Fan loyalty? What about owner loyalty. Wasn't it the Raiders that left OAK of their own accord? Chasing cash to LA. And years later, when that failed, chasing a promised 250M from in stadium improvements to get them back to OAK. Screwing the OAK A's stadium in the process. Feel bad for fans yes, but the blame is own the owners. The fans always get screwed. NFL goes where free stadium money with sizable markets dictate. One's yet to realize/or not caring they are getting played, bc the prestige is worth it to put their city on the map.
As far as the gambling, it's a non-starter. LV in NOT the sports gambling capital of the world, that has all moved offshore to the chagrin on LV. They made a big tactical biz mistake, back at the dawn of the internet age. They lobbied to stop online sportsbooks, where instead they could of embraced and controlled it. Be the mecca. Instead they became more worried about consistent profits, which sport gambling didn't always give them. They reduced sports betting limits to tiny amounts, drove out the big players, who move offshore and started their own sportsbooks. They cut the number of table games throughout, in others they implemented anti-advantageous player rules (6-5 Backjacks, 8 deck auto shuffling,etc) and concentrated on slots and other sure things. Now they are a sports gambling afterthought. More concerned with taking small bets and money from the tourist suckers.
BTW the NFL was built on sports gambling. Whether the want to admit it or not. The point spread was a NFL inspired invention. Much of the early NFL growth is directly attributable to gambling. So although they may never say it, they don't want to shut it down completely. Just look at fan duel today, you think the NFL cares about integrity and getting rid of that? Hell no!