Call WWE niche if you want, and sure its ratings are slipping, but Raw is still pretty much a permanent fixture in the cable top 5 week in and out. Eliminate the finals, it's probably ahead of the NBA, and certainly ahead of NHL and MLS on a nation-wide basis. Truth is, everything but the NFL is niche [in the US, calm down soccereheads].
Back when Front Row was open, they would draw a nice crowd for PPVs. If (big if I grant you) WWE can do the same and make Raw into a weekly event, that's 64 nights a year they're covered. Throw in 20 for football and maybe March Madness/NBA finals because out-of-towners in the parks don't care where they watch the game, you're at the same popularity as any other sports bar. Except a decent percentage of kids still want to come in during the day.
Finally, I'm sure there will be a gift shop that will make decent money off the WWE merch machine.
You may not like the product--I haven't watched it in years--but there's little doubt in my mind targeting the limited percentage of Universal fans who are into the WWE is not a bad bet. I think it has a much better shot at survival than NBA Sports Grill Brew, which also has a limited target market but far more competition in the immediate area.