Some people are extremely moved by their passion for God. I thought his tears were 100% genuine. He let himself feel the words of the song, instead of trying to maintain composure. Sometimes I also think the contestants are also very moved that they are able to finally perform in front of so many. Can you imagine your biggest dream coming true? Who wouldn't be a little emotional about that?
It's interesting that Jimmy thinks showing emotion is a negative, but the judges think that is extremely important. Maybe it lies somewhere in the middle. They need to never fake emotion. There are always going to be people who think the emotion is faked, but if it really is, it will probably be picked up by more people, and it would be a big turn-off.