Here is a contradiction that I cannot resolve.

POTUS has the authority to declass ANYTHING.

It would not be wise to do something just because you can because it could lead to impeachment.

If POTUS is protected from impeachment, then why not use his authority as POTUS to just declassify the documents and release them to the public?

This makes no sense at all. Clearly POTUS is afraid of impeachment because if he were impeachment proof, he would just declassify FISA.