Edgar has his number. Plus Penn never made any adjustments. Its his own fault that he lost. He's bread and butter is his BJJ. Not trying to stand a trade with a man who has faster hands and better footwork.
Penn had fallen in love with his hands. He met a fighter in Edgar would is just as good, and in the second fight even better with his. Penn seemed resistant to that idea and it wasn't until the late rounds in the last fight he tried something different. Even that was too little too late, and Edgar had an answer for him.
Edgar was taking Penn down at will. By that time i think Penn's conditioning didnt allow him to contest Edgar's takedowns. That said iv never seen BJ taken to the ground with such ease when he has arguably one of the best TDD's in MMA. Edgar simply tooled him.