The song hit home for Katy and she could relate to it a lot... she wanted to help spread the song's message to others who it may help, like it helped her. The song itself was inspired by Katy's own song By the Grace of God, one of the song's co-writers revealed. And, Greg Wells, who worked with the song's co-writers for The Greatest Showman soundtrack, is close with Katy and has produced most of her ballads (including By the Grace of God) and so really it's almost as if this song was destined to be Katy's.
It's gorgeous and I can't stop playing it. I don't see why people elsewhere are expecting it to be successful though. It's recorded for sentimental value, not to be a comeback single. It's not even being released via Capitol Records, but Atlantic, who she's not signed to. The song won't do anything unless pushed and I don't see Atlantic pushing an artist on another label's version of a 1+ year old song.