It's easy to miss, outside of Taiwan, one of the main functions of these visits, which is signalling to Taiwanese people and leadership that America is still present. The events of the last 18 months in Afghanistan and Ukraine have hit American credibility hard in Taiwan. It's practically impossible to EXPLAIN to Taiwanese people that these cases are different. It has to be shown, and weapons sales and congressional visits are part of of the showing. Seen through this lens, a Pelosi visit not happening after threats have been made would be disastrous (indeed, one might speculate, although I don't have the confidence to do so, that Biden saying publicly that the Pentagon doesn't want her to go is a way of amplifying the signal to Taiwan).