Most of them will work in music about as successfully as those of us who don't choose to be on such shows, and often, life takes over from time to time and leads artists and performers in other directions. Also, reality is,for mainstream "indie"/pop/rock/r&b acts in particular,even if you had chart success, after 30, you likely won'tand after 35, pretty much forget it, and after 40, not gonna happen unless you are a legend already. Yeah, some exceptions, but rarer than a genuine 3.5+ octave range on a talent show.The most dedicated (who have legit talent and/or are able to stay relevent)will find ways to continue and to be involved in their craft on some level no matter what else they have going on,It'snot always about being in the spotlight forthosewho love music .For every performer you see on the show, there is a team of dedicated artists of various nature , making them look and sound the best possible. Just because you don't see them doesn't mean more contestants aren't still working
The best of them were working before they won/appeared on the show, and will be after. The show gives them a big boost in promotion and exposure, and maybe financial backing. This lasts a few years at best.A really good, dedicated singer/artist who x factors will usually end up in the same place as the best of the acts that take what I like to call the "scenic" route .For those who could never have competed with the MANY great talents out there busting their arses in the real world who don't do theseshows and such, and for those who are that gifted and decide to go for it for a boost in career, the show can be a great window of opportunity.
It is up to them to make the most of that.
TLDR: The harsh truth is that the ones who are no longer working either 1-didn't have the talent or presence to keep enough people interested, no matterhow hard they may have tried. 2-didnt care enough/weren't dedicated enough3-sometimes, Life happens.That is no excuse, though. Many can return to music after a knock back or important life changing event. IF they choose not to, it might just mean they don't feel it is worth the effort, and that's okay, too, though most artists who are dedicated could never understand that.