Why was Joey Harrington drafted so high and why was he a bust?

coming out of oregon, harrington had all the tools that evaulators look for.. he had good height, what seemed like a good knowledge of the game, a strong arm, an accurate arm.. he was also benefited by a stellar performance at the combine.. but he proved that he couldnt put all the tools together and couldnt throw when pressured.. i dont think he is like carr.. carr was a one of a kind in the kind of hits he took his first few years.. i actually thought carr handled his situation about as best he could after being the #1 pick, coming to an expansion team, and having no talent around him..