Tsai is not entirely a creature of the US, and has indirectly - perhaps initially, inadvertently - manipulated the US by pushing for an unendorsed independence, forcing the US to deal with a situation they hadn't before considered - a 'two china' outcome.

However, now that US does sees this outcome, it cannot unsee it and is thus driving hard to secure that outcome, no doubt as a stepping stone for the long term goal of regime change in PRC

As for Chang, I think status quo is his ideal outcome - de facto independence, TSMC servicing two of the biggest economies in the world, and therefore, the entire world. Not happening now though, sadly