When the Chinese politburo gave itself the right to veto nominees for Hong Kong elections in 2016, it ensured that any future legislature on the supposedly independent island would be a puppet regime, its electors literally beholden to Beijing for their office; and by 2019, the puppet regime of Carrie Lam began to deconstruct Hong Kong's independence by introducing the "extradition bill," which would allow Beijing to demand that political dissidents be rendered to the Chinese mainland for show-trials and arbitrary detention.
The proposal by the tame, Beijing-dominated government of Hong Kong to extradite people to mainland China for a variety of crimes (including political crimes) sparked mass demonstrations that made savvy use of networks and tactics to mobilize a series of actions under the #612strike banner that shut down main arteries and key government buildings.
Hong Kong's previous mass-protest uprisings — 2014's Occupy Central, 2016's Umbrella Revolution — were ultimately smashed by the state through a combination of violent suppression and electronic surveillance, greatly aided by the hierarchical structure of the protest movements (which made it possible to decapitate them by arresting their leaders) and their internal divisions and infighting.
Hong Kong's 2016 Umbrella Revolution saw weeks of mass protests over a change to nomination rules for the city's ruling council, in which the central government in Beijing arrogated to itself the right to decide who could be on the ballot (Boss Tweed: "I don't care who gets to do the voting, so long as I get to do the nominating").
Three years ago, Hong Kong erupted as a youth-led anti-corruption movement called the Umbrella Revolution took to the streets; now, a chapter of the Extinction Rebellion movement has launched in HK.