Picasso and those others you mentioned all delivered the work. Eccentric? Why wouldn't they be--there are millions of eccentrics outside the arts.
I'm not saying there aren't flakes in the arts. I'm saying, the cliche has a basis in reality, but it's not the whole picture, not by a long shot. It's just been allowed to take over the impression of the art world due to repetition in movies and TV. If you don't deliver the work, you're not going to make it. Once you make it in ANY line of work, you are free to be a weirdo, and there are plenty of people in every line of work who become jerks or "quirky" once they've made it.
We're not disagreeing that much. Yes, once you make it in many lines of work you have more latitude in regards to behavior. However, the art world tends to indulge that behavior to a greater degree.
But yes, you have to deliver the work. The people I listed are extraordinarily disciplined when it comes to their work, it's other facets of their life that cause the mischief.
What I was not saying is that being a flake is a requirement for talent.