It flopped because the general public is pretty much over classic pop songs like ''Birthday''. It is more interested in alternative, rock influenced indie artists right now..
If it would have been released back in 2011, it would have been Top 5 by now already.
Not really.
''Dark Horse'' already reached #1 before the video even came out.
Completely different scenarios. Dark Horse was slaying since it was first released. It was going to smash with or without a music video. Birthday on the other hand was like a "brand new" single and the music video killed it.
"Birthday" slays! But Katy was just a bit overexposed after smashing with "Roar" and "Dark Horse". Give her a wee breather and she can release "Walking on Air", "This Is How We Do" or "Legendary Lovers" and smash yet again.
It was already struggling before the music video so don't blame that lmao.
It's kinda like "C'Mon", where it's an okay song (or great in the case of "C'mon") but there is nothing special about it. They're just run of the mill pop songs that blend in on radio and don't really send people flying to iTunes to buy them.