The key personality trait for achieving high agency is low ego
Low-ego people are almost entire focused on solving the problem, almost never care about appearance or credit while doing so.
Why low ego?
People with low ego are just much easier to manage. They tend to engage less in interpersonal conflict, they care more about achieving their goals than about credit or means.
Rather than getting caught up in status games, or credit-seeking, low-ego people channel their energy into solving problems instead.
One of the best feedback I received back in my McKinsey days was the following: from business perspective it doesn't matter who solves the problem as long as the problem is solved. That is when I realized I needed to dial my ego back, care less about me and care more about the goal.
Learning
Learning requires iterations, many of which will likely be failures. We need to discard our ego in order to iterate fast. We cannot stay attached to solutions that don't work, or only partially work, when discarding that particular solution would give us the ability to find a better one.
Teams and collaboration
It is far easier to manage low-ego people as opposed to high-ego people. The first group does not need any regular ego massaging in order for them to feel good and deliver well.
Breaking rules
When creating something new, we need to break habits and rules. When ego comes into play, for high-ego people appearance will matter more than the solution to the problem. This problem does not exist in low-ego teams due to the lack of care for their ego, dues to their sole purpose is solving the problem.