If you haven't heard of Michelangelo, or Leonardo Da Vinci I think you have been living under a rock your entire life, or you were born in a third world country with little access to any kind of education. These two artists, among others, have been part of our common everyday life, or at least mine. Their art pieces have been used to decorate gift bags, umbrellas, wrapping paper, ect, ect.....
These "masters,' began originally as commissioned painters or sculptors by either private families, clergy or the Church. I refer to them as "masters," because my personal opinion, is that any one person that is defined a "master," that would be he or she's life work. Their life's work would have been artistry, sculpting or painting, or other mediums. Now, in the modern era, people have business careers and painting or other forms of artistry as their "hobby." It's high competition and there is little money in it if you are still living. Most artists become famous after their deaths. Long after their deaths.
I believe that the artists of the renaissance and baroque periods moved from "artists for hire," to art stars, was probably the spread of word. People talk and can spread rumors or can spread popularity. It also doesn't help if you were commissioned to paint the ceiling of St. Peters Basilica in Rome, the "center of the universe" at the time.
In our modern times, supplies and knowledge of artistic production is so obtainable and easily accessible that I don't believe that their are any "masters," in this time period. I think people spread themselves out into different mediums and don't ever really "master" one technique. I think that there are more "art stars." than masters. One more popular example would be Andy Warhol. His bizarre lifestyle and underground social culture became popular because of the media, and also because it was the 60's and 70's. Outlandish seemed to be the theme of those decades. I think that a lot of art is starting to go into more of a "shock" medium, than any actual real classical talent, which, when that happens, history seems to always have a way of bringing in a new style, a new technique, a new kind of revolution.