The guy has been the champion for years and years, longer than anyone else has ever been champion.
He's had the odd high PPV buyrate here and there, sometimes supported by the right opponent and undercard...but he's never really broken out as a huge star himself. My 'non-MMA fan' friends know GSP and don't know him(one also didn't know GSP had ever lost)
A lot of it just seemed to be that every time he started to build a lot of momentum, something happened, a bad fight. Bad word of mouth is several times as potent(there is some type of research to prove this) as positive word of mouth. If someone loves something, they might tell 5 people, if they hate it, they'll 'warn' closer to 20.
The Cote fight wasn't very exciting, and then his very next fight was a '5 round stinker', whether it was his fault or not. He put on a truly epic performance against Griffin, but then follows it immediately with the Maia fight.
But the last 3 fights have been great. Chael talked the talk and walked the walk and Anderson pulled off a comeback that is the stuff of legends. He took Belfort out with a kick so awesome and rarely seen as a knockout blow that an entire wave of fighters have tried to use it to rock and KO opponents since....people call it 'The Anderson Silva kick'
He deconstructed Yushin Okami in front of his home country, avenging a loss and pushing himself into mega-stardom there.
Now he has a rematch of one of the most memorable fights ever ahead of him. Both Sonnen and Silva have been more vocal than ever before for this fight, which is great for promotion amongst PPV buyers...the UFC has not wasted time to take advantage of this.
They've cut promos using Silva's uncharacteristically angry rants. They even FINALLY gave him a primetime special, even if it was only on Fuel. Myself, my father(who hates Silva) and many others still watched it through the miracle of youtube. So even though it wasn't broadcast to the widest audience...it still was SOMETHING to help build the fight.
It has been over 2 years since the last Anderson Silva fight that wasn't great. I would bet there is an entire mini-wave of fans who only know Anderson Silva the ultimate comeback artist, Anderson Silva who 'trains' with Steven Seagal, who taunts his opponents at weigh ins by wearing masks, who gets a kick named after him, who makes the cover of a video game, who is a megastar in his home country, and who promises a brutal beatdown of his disrespectful nemisis, who only seems to keep winning and doing so impressively.
And with each impressive memory, not only is he building his highlight reall and further distancing himself from the Maia and Leites fights...but he also is just coming off as that much MORE relevant and impressive. It's one thing to be the longest raining champ on a 12 fight win streak who has had a few kinda crappy fights. It's another thing entirely to be Anderson Silva on a (potentially) 16 fight win streak who has done nothing but tear it up the last two years.
THAT is the Anderson Silva with massive star potential. I don't know if 148 will set any kind of buyrate record...but I don't see how it doesn't do a number that is at LEAST above average, and if Anderson wins with an impressive performance...that'll just go even further toward him becoming a PPV seller. Because if GSP has proven anything, having a completely non-existant personality does very little to 'un-star' you once people beign to tune into your fights en masse.
Could you imagine if at 37 years old, after being champion for so many years, that for maybe his last 4-5 fights, Anderson started pulling in 800K+ buys every time out?