What are you talking about? Dunn was never made out to be the clear number three pick and Ainge reportedly was considering a number of players.
Bender was talked up as number 3 for a long time.
You don't understand how Ainge and the Celtics draft clearly anyway. Always have their own rankings which looks far different to anything tossed up in the media and tend to always choose the best player available on their own draft board.
Brown was the best player in Boston's eyes and they drafted him. Sorry, but just because you claim Dunn is already some kind of ridiculous talent that we shouldn't have passed on, doesn't mean it's true. He could turn out to be better sure, but quit acting like there's some huge talent gulf.