I dunno, Vitor Belfort feels like a bigger name than people think. Some may not have seen him fight but he was pretty damn infamous in the early days of the UFC, with his name permeating the mainstream to a mild extent. He's got some decent name recognition.
There's certainly more money in a Sonnen/Silva rematch, but the whole title picture there at middleweight is strange. If Silva beats Sonnen and it isn't Belfort up next, then it's likely going to be someone that Silva already beat, if not destroyed.
Guys like Okami, Maia and Marquardt are where they are right now because they showed they couldn't hang at the top, all of them losing badly to either Silva, Sonnen, or in Marq's case both. Maia beat Sonnen but was laughably ineffectual against Silva, in a fight I hope we never see a rematch of. I don't think Belfort belongs there just yet.
Belfort/Sonnen would be the right fight to have within the next few months to properly settle contendership. Maia's got a fight coming up August 28 and Marq has a fight in September, so if Belfort waited to fight them he'd just be burning even more time. Dude's not getting any younger. He could fight Okami, I guess, but meh. Before the Munoz fight Dana White was saying that Okami deserves a title shot, so it's possible we'll see Belfort vs. Okami for the #1 contendership. Actually that seems likely, if they go with a Sonnen/Silva rematch.