People only vandalised at first. Some actions by protesters were over the top to outsiders, but they came after many peaceful protests and after police and triads colluded to attack protesters[2] (the producer of this documentary was arrested and charged). Protesters had to protect themselves at least at first.
In short, China tolerated peaceful protests in Hong Kong for a reason - they did no damage, and the government could safely ignore them and pretend Hong Kong still had autonomy. Once they had impact, authorities were quick to silence the people by any means.
[1] - https://www.info.gov.hk/gia/general/201906/09/P2019060900587...
[2] - https://www.rthk.hk/tv/dtt31/programme/hkce/episode/706428?l...
A nuclear power with 9000 tanks don't need reasons, let alone one which did many worse things with even less remorse.
How is the West supposed to make that happen, against a population that is being actively brainwashed? Almost all ways of entering information into China are censored.
For any protest to be successful, one side has to eventually reach a compromise. When the protests first started in 2019 for months they were peaceful. This was actually the time when they were the scariest for the CCP as its very hard to justify any action against them. Heck, I had friends who were PRC nationals who crossed the border to take part in them (just because they were curious what protest was and no other political reason whatsoever, and yes, they're alive and fine right now). The problems started when a few people displayed xenophobia towards PRC which unraveled into violence. At this point it became incredibly easy for CCP to smear the protests back home as all they needed to show in their local media was the few instances of violence against PRC nationals, juxtaposed against images of their own soldiers who were shown sweeping streets. Once England and USA started making comments about the human rights situation it was essentially a death knell for the protesters. This is because in China many consider USA and England's human rights comments hypocritical given that both countries grew economically by exploiting slaves (in USA's case) and colonies (in England's case).
Personally, I don't think politicians making bold statements from countries halfway across the world will help at all. Xenophobia overseas will make the matters even worse. Rather than turning anti-China and uber-nationalistic what would dismantle the CCP is to actually work towards winning the hearts of the 1 billion+ population, majority of whom actually have benefited from the CCP's reign.