China wanted HK to be special and successful, to use it as a showcase for the 'one country two systems' model. Now China just want to not lose HK. Huge change in thinking.
You miss out the last part, the British governor would actually listen to the people.
HK had almost 95% of what defines as democracy, freedom of assembly and speech, inclusiveness and equality, membership, consent, right to life and minority rights. It is only missing some part of voting.
> In 1946, shortly after the war, critical voices were raised against colonialism. Governor Sir Mark Young proposed a 48-member Municipal Council with significant competence to govern, one-third elected by non-Chinese, one third by Chinese institutions and one-third by Chinese individuals, known as the "Young Plan", believing that, "to counter the Chinese government's determination to recover Hong Kong, it was necessary to give local inhabitants a greater stake in the territory by widening the political franchise to include them."[9] The reform failed because of much resistance from expatriate companies, a new conservative and mistrustful governor, and London's fears of Hong Kong becoming a political battleground between the Kuomintang and the Communist Party of China (CPC).
But HKers aren't even asking for full independence. They want to retain the democracy and freedom they've had so far.
And the parallels with Soviet Union's collapse is debatable. At that point Soviet Union was on the brink of economic disaster, while China is at the height of their military and economic power.