Bold> The missing keyword is 'often'. Dak Prescott was not an abnormality. He was simply the latest (at that time) of rookie quarterbacks for playoff caliber teams, who became the starter either through injury or because they were drafted by their front office for the sole purpose of becoming their new franchise quarterback.
He joined that select list of 'good enough' teams like those led by Ben Roethlisberger, Mark Sanchez, Brock Purdy, Joe Flacco, Shaun King, Jayden Daniels, etc. Every rookie quarterback led team has exited the playoffs before the Super Bowl. What was and still is an abnormality was the presence of the just benched starting franchise quarterback on the same roster as the rookie quarterback for the playoff bound team. That particular circumstance was far rarer by comparison.