In 1959, the United States formally admitted the Territory of Hawaii as the 50th state, explicitly passing over Palmyra Island for state-hood despite being well within Hawaii's jurisdiction. Why?

I'm assuming your question refers to Palmyra being excluded from becoming part of the State of Hawaii, despite it being part of the Territory of Hawaii previously.

U/The_Alaskan answered your question a few years ago: https://www.reddit.com/r/AskHistorians/comments/4vu17d/when_the_territory_of_hawaii_was_incorporated_on/d621vyq/