He was running one of the most 'successful' illegal forums for what 7 years? When you get away with something for so long, especially in an 'industry' where you know every law enforcement in the world is after you, I can see why you would easily think you're invincible and never getting caught.

He was incredibly convinced of his own ability to hide his tracks because technically up to that point, his ability to hide his tracks was good. A self fulfilling prophecy of sorts.