For example right now a duo are preparing to do a manned space flight, which would have been unthinkable 30 years ago.
2 of them are described as "Lead" which is contrary to the point you want to make: "You Weren't Meant to Have a Boss."
Additionally the problem of putting someone in space is different from putting someone on the moon and back again.
I find myself thinking of SpaceX, which is tackling a real challenge and "big problem". They have, according to Wikipedia, more than 1250 employees.
That, along with the trend of software being used to solve more and more problems (more stuff is being solved by computers), it would seem like that eventually, even something like spending people to space would only take a small team, as infeasible as that seems right now.
To farmers of yore, it would seem laughable that we are able to produce a lot of food with so little farms. To builders of yore (like pyramids), it seems laughable that we're able to build taller buildings with much less people.
Given that technology and pace of innovation keeps accelerating, we should be able to solve larger class of problems with less effort and less man power.
Taking this trend to it's extreme , when we have human equivalent robots and AI , one man could build anything he wants by commanding machines to do the work.
The jury is still out on that one. The trend lately has been in the other direction.