TSMC always understood this. This wasn't a realization as the cost benefit analysis is obvious: US workers don't have the skill involved and they demand higher pay. The combination of the two makes the US plant a net loss.
TSMC did what they did because of political pressure. So the plan was always for the US plant to just satisfy that political pressure as much as possible. There was never a plan for the US plant to do anything profitable, it's more of a forced "technology transfer".