Why is commander so much more popular than oathbreaker?

Back in the day planeswalker cards were abundant. Even today they aren’t that expensive because of past overprinting and the war of the spark set. And oathbreaker decks require 40 less cards and thus the games go faster. So why did commander become overwhelmingly dominant to the point that you can hardly find oathbreaker events at your local LGS? You’d think the format would be more popular and have more support than it currently does.