The writing was on the wall well before it was even handed over. England was in no position to defend the island after the lease on the New Territories ended, nor are they capable of doing anything to prevent the CCP from slowly eroding institutions in Hong Kong now. Everyone else has little to no skin the game to risk anything significant. Their only hope was the belief that the economic development of China would usher in democratic reforms, which hasn't happened.

England never had any leverage in negotiations, so it makes sense that the CCP wouldn't care or honor anything because they correctly predicted that repercussions would be minimal. Over time, the importance of Hong Kong as a financial and economic hub/ gateway to China has waned substantially, so now the instability in the region isn't as costly anymore. The incentives were never there for the CCP to act in good faith.

It is incredibly unfortunate what is happening, but realistically it was only a matter of time before these things happened, the terms they agreed upon weren't much more than window dressing to allow England to exit gracefully.