The product is hot, but honestly it's just a bonus when it is. They were doing just fine before they got hot, not making as much money of course, but you have shows like Mania and the Rumble that sell out before any matches are announced (well the Rumble always has at least 2 matches announced, but you know what I mean).
Of course Vince is a shitbag of world class proportions, but he is also undoubtedly the greatest wrestling promoter in history. He got WWE to the point where it was basically idiot proofed by getting massive TV deals, and then getting Endeavor to pay way more than anyone thought to buy it.