In every case, there are times where someone can make something of themselves, or not. Personally, I don’t understand how a parent would allow their kid to be exposed to such peer pressure to begin with. On stage of hundreds, and views of thousands- if not more.
Besides, shouldn’t the kid be in yeshiva studying?
In making a chillul Hashem, if you go to You Tube and look at some of the past seasons- there are all kinds of crazy walks of life on this show. If one who is frum; shomer shabbos etc. and can do a good a job singing and make it to Vegas, why not!
L’Ma’aseh- the show is about ratings, the judges are there to promote the ratings, what they say increases their ratings of the show. Not always does it depend on who is singing, but the reaction to the judges. And sometimes, the reaction to the performers. That being said, if indeed, he reacts b’kavodi’k to the judges and accepts what they have to say without being disrespectful, and thanking the crowd for the opportunity, then by all means, it can be a very big kiddush Hashem. Also,
then of course, you have the she’ilos of shabbos and if the recordings have to be on shabbos or not, then kol eisha for the other contestants, etc. Going to a theater… and all those other takanos. But, for that – you have to ask your local orthodox rabbi.