A totally quick recap to those who don't know what happened in Hong Kong between early June 2019 and January 2020:
Hongkongers were promised by the UK-PRC (CCP China) handover treaty signed in 1984 that after the handover to PRC sovereignty in 1997 HKG would retain its civil liberties like freedoms of speech, media and assembly plus political autonomy with *universal suffrage*.
Initially after 1997 there remained a semblance of democracy although the legislature was always preloaded with indirectly 'elected' seats guaranteeing the CCP-aligned "popular minority" control of the legislature. Furthermore the all-powerful "Chief Executive" (essentially a governor) was supposed to be elected by the people but CCP "re-interpreted" the treaty to allow *itself* to choose the candidates! ¯\_(ツ)_/¯
Hong Kong continued to function as Chinese dictatorship's banking colony and as a powerful tool to play around the international trading system, but instead of making progresss towards the promised democracy through universal suffrage and especially after Xi Jinping took power in the PRC in 2012 the CCP stooges running Hong Kong began rolling back Hong Kong's civil rights.
In early 2019 the "HKG govt" announced they were going to change local laws to allow "suspects" to be extradited to the notoriously unjust PRC to be convicted in CCP's kangaroo courts.
Thousands marched but the "gov't" ignored them. By early June 2019 there were tens of thousands protesting, and the HKG regime set its police force to teargas and baton-charge the pro-democracy crowds...
People were outraged and the crowd grew to hundreds of thousands marching orderly through the city's long main avenues despite the draining heat and humidity.
On June 15 a demonstrator known as the Raincoat Man (Marco Leung) fell of a high rise building during a protest. The following day saw a record *2 million* people flood Hong Kong's roads. Out of a population of 7+ million.
There would be several million+ marches in the following weeks and months, but the steadily increasing *POLICE VIOLENCE* and various legal and other threats by the regime would start scaring regular people off from joining.
(Note: my avatar here is an ambigram character combining 警 'police' with 暴 'brutality' — ACAB only applies in authoritarian states)
All the while the local regime ignored people's "Five Demands, Not One Less" and cracked down on any peaceful pro-democracy activism ever harder.
A law banning *masks* was enacted on Oct 4. A few months later when Covid-19 hit HKG masks would be both banned and compulsory... 
Anyway, violent police crackdown, zero compromise by the regime and later strict Covid rules (no gatherings above 3 people!) would ensure that protesting was not only futile but criminalized. The regime was engaged in a "WHOLE PROCESS CRACKDOWN" on all remotely democratic activism.
On 30 June 2020 the HK puppet regime imposed "National Security Law" (NSL) on the city; essentially anything the CCP considers threatening or 'insulting' to its dictatorship was criminalized.