Have you ever taken music lessons?
Or received coaching for a sport?
What about learning to cook a favorite dish?
How to you become expert (or even moderately proficient) at any of the above?
Practice. Practice. Practice. And then some more practice.
While natural talent and ability gives immeasurable assistance — the best in their field practice, practice, practice. It does not matter if they have a world-wide reputation for excellence. To keep that standard they practice.