While the Rock gets most of the credit for 28s record buys, Kellers theory is that in in actuality not having a UFC PPV within like 2 months of mania was what made the difference between a decent buyrate and the record breaker we got, NOT the Rock. The idea obviously is that the companies share a fair amount of fans and most of those fans have to choose between WWE and UFC most months since we're not dropping a 120+ a month just on PPVs. Since UFC was nowhere in site last year during mania all those fans just gave Vince their money.
I originally scoffed at the idea since I didnt think they competed that much in PPV and since we're programmed to think of Rock as the biggest draw left in wrestling, but all of Rocks other headlining PPVs since his return have been disappointing (atrocious Survivor Series, disappointing Royal Rumble, and assumed disappointing EC.), so this theory tends to hold water in that regard.
PS…have u looked at the trend in UFCs buyrates last few years? There's a big drop that coincides at the time Brock was leaving. Not the biggest UFC fan so don't know if there's more to it.