Studies have nothing to do with it. If you're a Nevada politician, you can:
a) Vote to build a big tourist draw that does not compete with the existing casinos/resorts (and actually helps them fill rooms...meaning casino owners will appreciate the favor, perhaps to the tune of campaign donations) and be able to claim you voted to create a bunch of jobs
b) Vote against and get to claim you are fiscally responsible because there is no proof it would pay off for taxpayers. (Then defend every other expenditure against the "we could have had the Raiders and a stadium" argument.)
Right or wrong, its fairly easy to see why this was a vote that was destined to pass.