Why are Chinese people quiet after the flag-hissing ceremony at Tiananmen?

I saw the ceremony in the morning. There were thousands of young people who arrived in buses and there was a long line to get inside the fenced space near the flag. People were excited as if it was a rock concert. Then the soldiers marched in, they hissed the flag, they played the anthem, and then the soldiers marched away. I was expecting that after the anthem finishes, the crowd would burst out into a cheer or they would at least applaud. But nothing happened, everybody remained quiet, and the crowd disbanded. So much excitment before the spectacle, and when the spectacle is finished, they do nothing.