I think this was instrumental in their success - older people are more cautious their approach. Younger people don't know what can and can't be done and are way more Liberal in taking risks.

I also think of this as related to the second system syndrome - Apollo was the first system for a lot of these engineers, and doing lots of things for the first time ever. People were bold and cautious at the same time. The Space Shuttle was the second system - an way over engineered system that did not reach the targets it was designed for, and was successful only through large amounts of money being thrown at the problem.