Would we know Thalberg as we do now but for F. Scott Fitzgerald’s fond but observant “The Last Tycoon”? That unfinished novel gives a brilliant picture of how Thalberg looked after about 50 pictures at a time, while keeping Louis B. Mayer and Nick Schenck at bay. Everyone always said Thalberg was going to die young — he was small, fragile, dark and pretty funny. He also had education, taste and instincts way beyond those of Mayer. That said, in his great years at MGM, he pursued safety, high ideals, higher production values and the most complete version of the dream called movies. And yet, there are few unequivocally great films that “belonged” to him. He married and promoted Norma Shearer; he restrained the Marx Brothers; he loved monsters like Lon Chaney and Charles Laughton. And somehow he stands still as the ideal model of efficiency who also insisted on just a few difficult, dangerous pictures that might change the world — and ruin the studio. Yes, he died young: It was that or be assassinated.