Why did Chen fail to win the men's rings final in this Olympic Games?

They are all referees. I really don't understand: Chen's movements are not worse than those of Brazilians, even much better! Brazilians are still swaying in their movements. When they come down, they will retreat 1 small steps. Chen won the silver medal, which none of us expected. Most of us think that Chen will win the gold medal. Chen's score is 15.8, while the Brazilian's score is 15.9, which is really unpredictable ... Although Chen didn't win the gold medal, he still has a smile on his face. I think this is more important than the gold medal! He can face everything calmly, why can't we?