Newk was a great grass-court player and what's more, he had the smarts. Newk was 30 and an experienced big-match player, still at or near his peak. He had been around the game a long time. Like Jimbo said, Newcombe also had a lot of pride in himself, and in front of a home audience too.
John had played himself in at the Masters just previously as well, knew the courts and Connors was cocky back then,22. We know what Jimmy was like back then. This match was a bit like Ali v Foreman where Ali out-thought the powerful young Foreman. Experience. Newcombe had the big game to give Jimbo a grass court lesson. Connors got some smarts himself later on.