POTUS has the power to declassify anything.
Trump exercised his power by doing so. No permission is required. There’s a legal case on this topic (Obama era, I believe) and that’s the law.
Total nothingburger and selective political application to smear Trump now that he’s announced again.
Where’s the Special Prosecutor for Obama, Joe Biden, Hunter Biden, Pelosi, Romney, etc. etc.?
Which, of course, is not the point.
Declassifying something doesn't make it less sensitive.