That isn't the secret to his intelligence. The secret is Dr Doom uses time travel to know the future and has traveled back in time many times Then simply waited out the years mastering different fields of science using magic to extend his life He's also got a time loop device that lets them relive the same day over and over again. He's also traveled to future to get future insight and future technology to add to his own tech. The Author of this article is pretty much trying to damage the brand of character. Dr Doom is literally spent thousands of years developing different skills. Example is he spent centuries with Morgan Le Fay. Both romance her and learning magic.