The idea was to reduce trade barriers within the Pacific region, which would make trade there cheaper and hence more attractive vs China.
Specifically, lower wage countries (Malaysia, Vietnam, Mexico) would have been more attractive as outsourcing locations compared to China, and in return good and services from high wage countries would have been cheaper in those countries making them more attractive compared to Chinese competitors.
As a specific example, most industrial machinery imported to Vietnam is subject to a 20% import tariff[1]. This means US companies like Caterpillar and GE are relying on political intervention to win deals[2], instead of being more competitive on price.
[1] https://www.customs.gov.vn/SitePages/Tariff-Search.aspx?port...
[2] https://www.thegazette.com/subject/news/nation-and-world/us-...