Idol completely abandons the contestants after the show, especially if they don't get signed and a team together. I can imagine it can be very dark for their mental health. You've been on a high for a few months and out of nowhere, nothing. Pia Toscano talked about life after Idol on that reality show she was on on Netflix. She was on a high, touring, released her single, signed a major record deal, fame, etc. to literally no record deal, her album shelved and she couldn't pay her bills. She said how basically everything suddently stopped and she was alone.
To feel like you have it and all have made it to literally everything stopping must be very hard mentally. It would be for me.