Why was the launch and fail of 'Project 571' something major in the history of China?
Anytime there is an armed uprising within a country, it is deemed a major historical event. It seems China is no exception. In fact, China has quite a few turbulent events in its history. Of special importance, however, is any event targeting top military or political leaders.
It seems that no matter who's in power or how bad or good they are doing as a leader, there's always some group who thinks they need to be eliminated. This creates civil unrest and can lead to catastrophic results if the insurgents accomplish their aims. Military insurgents are the worst, often using their own internal forces originally intended to keep peace and protect.
In China, the rise and fall of Project 571 shaped their future in many ways. It showed that anyone, no matter how high up the political ladder they were, was capable of treason. It showed that "you can't please all of the people all of the time." It also showed how vulnerable all the political parties were and the devastating consequences of mislaid trust and loyalties.
I believe the greatest lesson learned from the failure of Project 571 to accomplish the assination of Mao Zedong was that no leader is infallible and totally supported within a Communist regime, and sooner or later, someone is going to challenge the status quo.