Now, I've got nothing against Rihanna. I've heard of her. I've heard her voice and like it. I've definitely heard a song about an umbrella, although frankly the only version of it that really earwormed me much at all was performed by Fall Out Boy at (IIRC) the Grammy Awards show one year.
But I have to question any metric that ascribes more "star power" to her than to (among others) Michael Jackson, Stevie Wonder, Aerosmith, U2, Paul McCartney['s doppelganger], Prince, Tom Petty, Bruce Springsteen, The Who, Beyonce, or Madonna.*
Is Rihanna really that popular by comparison to those artists? I find it hard to believe.
* None of whom performed at my favorite Super Bowl halftime show performance (among those I've watched, which isn't many of them): The pretty low MARIAH-ranking Red Hot Chili Peppers in 2014. Love'em, but I'm willing to believe that on some notional "star power" metric, like name recognition or numbers of best-selling songs/albums, they're an outlier.