This is a pretty thorough rundown of what happened [https://en.wikipedia.org/wiki/Guantanamo_Bay_detention_camp#...]. It appears an earnest attempt was made, but was blocked by a republican-held congress.

During Trump's first term he signed an EO to keep it open indefinitely.

Even if Obama had closed it, do you think that would've dissuaded Trump from reopening it to create his freshly-minted, extrajudicial concentration camp?