Initially, when the idea is small, it is hard to sell it to talent, investors and early customers to bring all key pieces together.
Later, when the idea is well recognized and accepted, the organization usually becomes big and the challenge shifts to understanding the complex interaction of various competing sub-ideas, projects and organizational structures. Humans did not evolve to manage such complex systems and interacting with thousands of stakeholders, beyond what can be directly observed and fully understood.
However, without this organization, engineers, researchers, etc cannot work on big audacious projects, which involve more resources than 1 person can provide by themselves. That's why the skill of organizing and leading people is so highly valued and compensated.
It is common to think of leaders not contributing much, but this view might be skewed because of mostly looking at executives in large companies at the time they have clear moats. At that point leadership might be less important in the short term: product sells itself, talent is knocking on the door, and money is abundant. But this is an unusual short-lived state between taking an idea off the ground and defending against quickly shifting market forces.