Surgical training can be 4 or more years beyond medical school. The bio never said "board certified". trained does not equal qualified surgeon. He probably did drop out of the long process for better opportunities.
Actually, surgical residency is a standard 5 years past medical school. ACGME requirements. Two-three more if a fellowship/specialty desired. Mooney only did two years. However, note from the Hard Rock presentation, in his introduction after giving his name, Mooney says "I am a suregon by training." Go ahead, don't take my word for it, play it and listen. I'd call it overtly deceptive and indicative of the way he deals in other realms of business.
Why he left? Who knows? Dropout, possible. Better opportunity, possible too--he suddenly may have found the position on "Wall Street" more interesting than medicine after all those years. Then on to cancer mabs, failure at APHT, then the dog and pony show here-- a real cursader for diabetes who wants to run the share price up and sell out--as he has stated before. IMO, it is apparent this is a guy who is not passionate about the true cause of the company he runs, and sees medicine and the market as a means to self enrichment. His heart is in his bank account and hand in your wallet. believe me, this is a guy who could care less about those with diabetes, and the common shareholders who own the stock, lol.
Whether he dropped out or never intended to obtain the full education, I don't believe matters. He has an MD degree and knows much more than me. I'm not sure why a surgical degree seems to be a requirement.