Running is the most useful mechanism to arrive at the conclusion that you are capable of so much more than you think you are.
Those self-limiting beliefs are what is holding you back dramatically in living the most fulfilled and colourful version of your life.
Running is not inherently linked to Arc Project. It is just a useful mechanism.
If intense synchronised swimming was the revelation-inducing activity that delivered people the same revelation as ultra running, then we would be doing that.
Running an ultra marathon is a liberation from thousands of other self-limiting beliefs that you hold about yourself, to stage a personal rebellion.