In smaller startups, everyone is directly involved and has to punch above their weight to pull through, not just the CEO.
Also devoting everything in your life to one thing is not a mark of intelligence or skill. It is a mark of dedication but by itself means little.
And yeah, not everyone can be a CEO because most business fail very quickly. There is always an element of luck in those that survive.
But the idea that you devote 24x7 of your life hence you must be a good leader is not accurate. In fact, if you press this culture downstream, you'll tire your workers and the rest of the team.