Not to condone his actions, but it is not like he did not have a Commercial Pilots License, from reading the article he is a fully licensed Commercial First officer in type. But did not have the final qualifications to rate him as a Captain.
It reminds me of what one of my favorite collage professors once told me. That at least 10% of all people doing any job have no business actually performing it. And he included Professors, Doctors, Police officers, and Pilots. It always stuck with me. But ultimately you have to trust the system to police itself. I found it mostly worked in Aviation in my experience, but sometimes takes longer than it should. Sometimes much longer.
In this case the system did catch up, but years after it should have. I have found that individuals that this apply to, usually have political of financial influence over the organizations that let it "slide". In one case the son of a highly respected former CEO of the company, and he flew for the small airline for years, with no issues, a natural Pilot, the only problem was he never finished his commercial pilot training. The issue was finally uncovered when they went to promote him to Captain. And a routine paperwork check found issues.
It was covered up quietly, he was fired, and reported to the FAA. I do not know what happened after that. This was in the 1980's so it was a different time.