If I'm putting on my cynic hat, China is thinking long term about Taiwan and couldn't give a fuck about Ukraine. They've probably just arrived at the need for a certain set of circumstances being what they need in place.
- They don't want a Russian collapse and they see it on the horizon. A "stable" Russia is a key supplier of raw materials for their economy. A basket case with multiple breakaway regions is harder to wrangle, and probably leads to significant supply disruptions, price disruptions, etc.
- They're not really interested in an economy equal to the size of theirs emerging as a strong competitor. Xi is stupid but he's not dumb. A weak EU is better for Chinese power projection. The Euro has the ability to become an alternative to the USD instead of whatever Brics fuckery they've been thinking of, and Europe is a natural ally for a few countries they would love to be able to boss around in a multi polar world. Namely Aus//NZ, Us, Japan, SK, etc. An EU with legit military might isn't going to be something anyone is going to want to fuck with.
- China has seen what it needs to regarding the ability of a determined defence to turn an annexation into a clusterfuck. There's nothing else for them to learn, it's all cautionary tale upon cautionary tale to convince themselves they can plan around.
- They see Trump getting a policy win in Ukraine as a good thing, even if he ends up having little to do with it in the end. Trump is forcing this TSMC move and the annexation of Taiwan isn't necessarily about capturing the semi conductor industry to the exclusion of everyone else (that's the easiest way to get the rest of the world to join in tbh). Let TSMC get enough fabs set up elsewhere that their invasion isn't a massive disruption to the world economy by shutting down semi conductor production. This is a cultural project with a technological benefit, not a tech theft at it's heart.