Younger girls have an advantage in gymnastics unlike some other sports. They are smaller, more flexible, better balanced, etc. Besides this, the Olympics see it as unfair to have younger athletes compete due to pressure, expensive contracts, etc. They believe that 12 year olds should not be professional athletes.
Whether you agree or disagree with this rule does not matter. It is the rule. Other countries followed the rule and one (China) supposedly diffferent. For this they should be disqualified.
And the silver medalist who now is getting gold deserves it because she was the best competitor within the rules.
And don't blame asians, blame communists.