Second, this administration has been promising a trade war with China since before the election. It's not as if this is some kind of surprise. "CHYNA!" was a major campaign issue.

For background: in the Nixon era, the USA decided that it would start a Marshall plan style trade deficit funded "investment" in China, with the belief that increasing the economic prosperity of the PRC would lead it to greater openness and generally becoming a tame satrapy of the US empire, much as Germany and Japan did. Now that it's clear that plan was a complete failure and the Chinese played the Americans for fools, some Americans, most notable among them the President, are looking to reset to a less inequitable trade relationship. Pretty much all major economic and political news from the pacific region is a consequence of this process. The Hong Kong riots? Turns out the CIA is involved[1]. North Korean missile launches? Yeah, how much real autonomy does the DPRK have when China decides to call shots?

Edit: [1] https://www.reuters.com/video/2019/08/08/us-calls-china-thug... (Obviously this is a pro-US outlet and frames it as innocuously as possible, but anyone who knows anything about tradecraft knows that "diplomat" in this context is a polite word for operative).