Unconditionally is a midtempo ballad that was released after a MASSIVE single that was still in the top 5. And it was also overshadowed by Dark Horse which got radio play and was considered Katy's new single. Also was released with the album, like who the **** does that. It was literally a mess.
Applause was the lead single, was a dance song made for radio, and was following massive hype and got a huge radio deal. It was expected to soar to #1 with like sales of over 500,000.
Both underperformed. Unconditionally didn't have the expectations that Applause did. So Applause