You have to be willing to share your responsibility and give up your expertise to be a great leader.
This was a quote from a friend of mine who leads a large organization that he grew up through the past couple decades and it caused me to reflect on my own journey (not claiming I'm a great leader here, just thinking about what I'm willing to give up in an effort to become better...)
I excelled because of my technical skills and ability to acquire knowledge quickly made me a "go-to" person. Not only did it make me feel good, if I'm honest, it was something I began to take identity from. We can get comfortable in our abilities and what we know but there's no growth in the lack of stretching and very little up-side long term. Being willing to step into the new role, skills, and context knowing that you're going to struggle, make mistakes, and maybe even fail can be both exhilarating and terrifying. With the right mindset though, you'll learn your way forward and be better for it.
It's only been with the wisdom of experience and perspective that hindsight provides that I can see the biggest growth is actually that which I've helped foster in others, not my own. I'm limited in my growth but when I grow beyond myself, thru others, I don't have the same limitations. Not confined to the singular meat-space that I represent but the larger collective that is the people surrounding me. Think network effort...multiplicative impact
I'm not saying that everyone who tries this will succeed, they won't. But that doesn't mean we shouldn't try. The really hard part is what do you do when you realize someone is not going to be successful? If you leave them there, you have a problem (read: Peter Principle). People are promoted to the highest level of their incompetence and because the managers are often not willing to let them go, they get shuffled around and around until they self-exit. It's awful for everyone involved. To avoid this, you should have an honest conversation ahead of time of what success criteria look like and what timeframe can be expected. Then, follow up on that conversation REGULARLY so things are abudantly clear on status and performance. It's super easy to write and even easier to agree it's a good thing but super hard to do.