Here’s all you need to know about Malcolm Nance: https://sofrep.com/news/a-matter-of-honor-the-fiction-of-malcolm-nance/
Bottom line: He was expelled from his own community, the Naval Security Group (NSG) in disgrace. Nance was assigned to the Navy SERE school in San Diego for his last assignment before retirement because no one in the crypto (intel) community would take him. And while assigned to the SERE school, he was not allowed to train SEALs or Naval Aviators.
Only MSNBC would take someone with such a checkered record and proclaim him an “expert.”
Addendum: note the timeline that is established in the article; Nance was declared persona non grata in NSG in ‘92 or ‘93; almost five years later, his detailer was placing him at the SERE school because no one in the Naval intel community would take him. And during that assignment, he was specifically barred from speaking with students in the Arabic courses at DLI (Nance was an Arabic linguist), and not allowed to train students at the SERE school. It was basically a dumping ground until he could retire....