Dealers like Daniel-Henry Kahnweiler in Paris used his livelihood to champion the early cubists and to showcase Picasso.

FORBES: The Art of the Deal

The Nahmads (who say they bought more than 200 Picassos from Kahnweiler's gallery) operate as secondary-market merchants rather than supporters of the arts.

FORBES: The Art of the Deal

Gregarious, engaging and comfortable in seven languages, David cultivated relationships with the likes of dealer Kahnweiler and billionaire art collector Baron Hans Heinrich Thyssen-Bornemisza, who bought works by Picasso, Kandinsky and Italian futurist Giacomo Balla.

FORBES: Magazine Article