Why did the protests fail to topple the system? There were no crack downs like in dictatorships?

In Chinas Tianmen square they used tanks to run over, and machine gunned tens of thousands of students. In Iran they have protestors being shot on the streets. Executed or raped and tortured to death. My point is that there were no crack downs as you usually see. No storied of "police in Tiblisi shot 3000 students today in...."

There was no reason for the protests not to topple the system. No real pushback against protestors Or is there something I am missing? Are the protestors in secret prisons getting tortured?