How do you think that well-known experts became recognized as experts? They focused on something that was interesting to them; they mastered the literature; and they develop their own experience so that they could make their own contribution. The result is a self-reinforcing process. The more you see, the greater the experience and expertise, the more you see.
I know how to take it off and keep it off.
Two. Hundred. Pounds. I’ve kept the weight off for over forty years.
This makes me an expert.