TPP was a brutally anti-Chinese trade agreement - it forged privileged trading status with all of China's main rivals and China would only be allowed to join later if they shaped up.

The US opted to drop it and unsuccessfully deal with the Chinese party 1:1 in negotiations. Imagine if a business partner was robbing you, and instead of finding other partners, you tried to negotiate with them. Obviously, they hold all the cards and have no incentive to play along. If anything, they would want to steal more! They would get more leverage!

I don't know if the TPP would have been a silver bullet, but it's hard to imagine the CCP would be this brazen if they were on the outside looking to come in. Remember that actions in Hong Kong and Xi Jinping's lifetime appointment all happened after the TPP was killed. I think they are power grabbing as much as they can now while no one is really holding them to task.