In my late twenties I got into the 24 hour endurance thing as I was bored with crit racing, and wasn't good at it anyway. The challenge of pushing oneself to the limit of exhaustion is addictive and difficult to explain. After a few years doing this I realized it was stupid for me to keep doing it. In no way was I anywhere near the super human these Divide Ride guys are! They are super human and super nuts. Not sure ego has much to do with accepting the challenge, well at least outward ego. There is just something that urges one to do, as though it has to be done. It is very different from triathalons.
I enjoy watching these videos as I can no longer do these types of activities. I do wonder how many years of a quality life in old age it takes from those that participate.