The Adelson angle was problematic from the start. Even if the other owners- or enough of them- could overlook the perceived risk of any professional team playing in a city in which the primary industry is gambling, there would still be other issues. For all its problems, the NFL does seem to conduct serious due diligence into potential owners. First, they have to have money- see Kroenke, Khan, etc...
Second, that very select group wants guys who play nice with the other guys. This is important because the NFL is essentially a monopoly- and successful in part because it can act as a monopoly. So long as a bunch of billionaires play nice with each other, they all win. That's why a moron like Goodell is there- he's the very well paid pinata for these guys. He takes the licks publicly, they make money behind the scenes. Flame throwers aren't welcome in that club because a guy like Cuban isn't afraid to rock that boat. Look around and there are no owners in the NFL who really act like Al did, or Cuban does. Some are incompetent dipshits, but few challenge the NFL directly.
Here's where Mark's relationship with Adelson would cause problems. First, Adelson is a massive prick. He's one of the most litigious assholes out there, and if his expectation was to put up money in order to own a large or eventually significant piece of the Raiders, I'd bet a number of owners would say no way because they don't want him at their table. He's richer that all but a few, and doesn't give a shit who he pisses off.
Second, as recently as three or four years ago, the DOJ was looking into Adelson's business dealings for possible violations of the federal law relating to foreign corruption. Nothing came of those, but that's the kind of red-flag that probably would kill any chance of the Raiders moving to LV, if Adelson was getting a piece of the team. No league would risk that type of hit, especially after the debacle with Haslem and his very well publicized Flying J scandal.
TL: DR version: Not sure the move would've ever been approved even if Adelson put up the cash, and Mark is back at square one. Either NFL kicks in real money when they realize that a stadium doesn't equal success (See Chargers/Rams in 2019), or Mark finds other sources of cash.