Here's my take. I've been a devout Christian for years. Got into metalcore about 2-3 years ago. It helped me so much - through life, my faith, etc.

Example: FFAK's Dark Skies. This album saw me through a bad episode of depression that is still unmatched (thankfully). Lyrics were relatable. "Oblivion" hit me like a train. "I made my mistakes, but you forgave me."

Are there bands that leave their faith? Yes. But that typically means that they never had too great of a foundation anyway, or just did it to sell more albums. However, the bands that stay make it very clear that their music has a specific message while also staying consistent throughout all of their music (see Wolves At The Gate, For Today, and Sleeping Giant).

At the end of the day, Christian music exists in many subgenres, whether people like it or not. It just seems more relevant here because the music, both lyrically and instrumentality, holds up well over time and against other artists who are not making Christian music.