IIRC, the 'Majors' term comes from a BOD Planning Committee, headed by Bill Kephart. They presented a plan to restructure National racing at the 2011 Runoffs. The driver for the plan was the proliferation of Nationals, which, combined with declining overall entries, lead to a dilution of the racing experience.
The main feature was to be a reduced number of Runoffs-qualifying events, renamed 'Majors' to distinguish them from the former 'Nationals'.
Additionally, the Kephart plan proposed events restricted to only the top 6/7/8 classes, each with its own run group. In the report's unfortunate phrase, this would 'cluster' competition. All the other classes would be relegated to events with alphabet-soup run groups. As you might imagine, this idea went over like a lead balloon, especially in more thinly-populated areas like the Plains states, and quickly died.
At implementation time, the Club sort of grafted Majors on to the existing Continental (now Hoosier) Super Tour.
Naturally, old patterns began to reassert themselves. In response to Divisional and Regional pressure, the Club created the Divisional path to the Runoffs, with Divisional races becoming the new Nationals (sort-of).
tldr: In its inimitable fashion, the Club 'simplified' racing by making it more complicated.
