Your sentiment that any effective or true leadership requires both humility and vulnerability is one that rings true for me. It’s an essential building block for high level leadership/servitude leadership. One among others.
Vulnerability (and humility) is probably the most difficult leap of faith to make as a leader that first time. But it might just be the most rewarding. As the universe dictates, Risk = Reward. Ultimately, risking being vulnerable is a leap that many simply will never take.
When I reflect back on my own leadership path and consider the leaders I had available to learn from, my own leadership development was guided far more by observations of how not to lead a group of people. Unfortunately this is true for many more people, as leaders everywhere fail to understand how it is that they can get the best out of their teams.