American Idol (etc) is actually a pretty interesting exercise in game theory.

The good singers know they need to keep something in reserve for the later rounds, but if they keep too much back then they get knocked out early.

Plus there are things like song choice - someone wants to appear individual and interesting so they need to choose unique songs. But they want to appeal to the widest audience possible, which means popular, well known songs. Trade offs are always interesting.

Try watching for a few weeks and you'll get the idea. Then you'll never need to watch it again, because you can reuse the same comments every year:

ohhh.. he thought he was so good last week and played it too safe/She should have kept that song for later when she'd built up a better fanbase/etc etc