When they saw how well Dark Horse was doing (radio, streaming and sales), they should have pulled Uncle's release before it even began. It could have smashed winter 2014 tbh. Birthday was released WAY too early (it never charted above DH in any given week), and when it was rising pretty strongly they came and dug its grave with that horrific video. TIHWD had no chance since radios were either already playing WOA or still playing DH/Birthday.
Another unfortunate thing (although completely irrelevant) is that Katy's hits always seem to go head to head with the biggest smashes of the decade (CG vs. LTWYL, TD vs. Just the Way You Are, Firework vs. Grenade, E.T. vs RITD, LFN vs MLJ and PRA, TOTGA vs. WFL, WA vs. CMM, Roar vs. BL and Royals, and DH vs. Happy)
, and even though i love Unconditionally (it's actually my fav of PRISM), It Takes Two should've been a better single, it even sounds like an Adele song 
I mean, Birthday was practically written to be a smash hit single; that's why Bonnie was like "I can't believe it didn't smash!" after it underperformed. 
