In essence

Why did Fitzgerald die a failure in his mind? The wavering and short-lived worldly success he did experience peaked and died away as he took other writing positions (that he didn't care for) to make money. It wasn't until the 1950s that he was placed among the ranks of great American writers. Why then and not before?

"What, then, ultimately differentiates Fitzgerald among the novelists of his time is his paradoxical clothing of a hard, ironical pessimism in a style that is soft and woven with a gossamer tracery. Yet, for all the peculiar excellence of the style, the range of his ideas remains hemmed in by the singular negativism of his view of the world and the dogged, unvaried way in which this is repeated from story to story — which further tends to pin Fitzgerald in the ranks of the minor writers."

— The Essence of F. Scott Fitzgerald, Leo and Miriam Gurko

In addition to this, the context of his literary works were not of interest in his time, around the Great Depression.