A reader asked me to write about common traits of leaders and successful people across different industries and fields. Of course there’s a famous business book that covers seven of their habits.
I’ll look at it from a couple different perspectives.

Functional skills hold you back at higher levels

Functional skills are ones to do a specific type of work, like sales, programming, engineering, marketing, and so on. Most people get hired for functional skills. They look good on your resume when you start.
A typical job progression for someone who succeeds at each level starts with a functional role and keeps getting promoted: a salesperson gets promoted to sales manager, who manages other salespeople. From sales manager they get promoted to a higher level sales manager, who manages sales managers. Eventually they get promoted to something like VP of sales, or some place where they manage all the sales people in the company, reporting to someone in general management, along with others, like VP of marketing, VP of R&D, etc.
A parallel trajectory happens for people starting in other functional roles.
What happens next illustrates a major set of skills for general management and leadership.
The person’s next promotion would be to general management, meaning people unrelated to sales will report to them—in this case, the VP of marketing, the VP of R&D, and so on. While most people succeed after promotions within their functional roles, research shows that of people promoted from functional management to general management, only half succeed. The other half fail at general management despite having succeeded at every stage so far and despite the selection effect that the people who promoted them thought they were the best person for the job.
No matter how useful your functional skills are for functional jobs, they largely don’t help in general management, where high-level leadership happens. Overly specialized skills can even hurt your performance if it results in favoritism toward what you’re familiar with, or even people imagining seeing it.
From another perspective, high level leadership requires skill unrelated to typical functional skills. This makes sense after you know, since general management and leadership means dealing with people and people issues largely disconnected from the objective criteria of a functional area. People issues are based in emotions, motivations, perceptions, relationships, and so on.
Caveat: Sorry, the best I can do to cite the research on the fifty percent failure rate is that a business school professor told it to our class but I haven’t read the original research. He taught one of the school’s highest rated class for a long time, so I found him credible, but he passed away. If anyone can point me to related research, please do.

Alternative perspective

Since business school, studying and coaching leadership has led me to stop seeing people skills, emotions, motivation, etc as the mysteries I once did. Since I see you can teach leadership, I’m starting to treat leadership as another functional role, just one that few places teach as a vocation, rather that most people think you have to learn on the job—hence the fifty percent failure rate. This unmet demand for leadership training combined with my clients’ success is a major motivation to the entrepreneur in me to start a leadership school to meet that demand.