I believe you are a bit mistaken about not being any demonstrations in China. Last year there were some 20,000 to 30,000 localized demonstrations across China against food prices, illegal confiscation of property, corruption and other events. Only the really big ones get noticed.
Remember the big demonstration about the girl who was mistreated by a cadre member in northern China. That got reported because it got ugly.
Most demonstrations are put down very quickly and are not reported.
I shall get references if you need them.
Welcome to the forum.
Demonstrations do exist in China but in the past years they are seldom reported to the public. But with the develop of Weibo(Chinese Twitter), we can got these news quickly. The bomb blast event is now being forwarded on the internet.
The number you mentioned still shocked me.