I wasn’t like schools on the west coast could just pop over to Princeton and play a game on a Saturday afternoon in 1920. Of course the east coast schools won all the championships because they organized them. It’s like saying an American baseball team always wins the World Series or football team always wins the Superbowl.
When more schools were able to travel, more schools outside the east coast region started to win. Read “The Boys in the Boat.” Even in 1936 it was very difficult and expensive for teams to travel to the east coast to challenge the “National Championship” teams.