Another "core" view - Rachmaninoff, This Time!

In perusing the very marrow of the bones of the works by Mozart and Beethoven in recent blogs, I find it really difficult to forge a way to describe, in most composers, a view, not of the style, but of the very raison d'etre of the music. May I try Rachmaninoff?
After Scriabin, Rachmaninoff emerged, first in his shards of the "post- mysticism" of Scriabin, but in truth, as the totally self-sustaining composer, especially after his sessions with the suggestive hypnotist Dahl.
To make mercifully brief my encapsulation of his core, from which radiates the music we know:
After all, Rachmaninoff almost makes it through the first half of the twentieth century(he passed away in 1943). This tall, gaunt man stood tall in the midst one of the most violently transitive periods in musical history, which began with Schoenberg's suggestion about the destruction of the key-signature. What with the likes of Stravinsky, Bartok, Hindemith, Prokofiev etc., each with his own school of followers and detractors, this tall, gaunt man, long after the peak of 19th century Romanticism, stood tall as a true Romanticist, and with a language truly belonging to him.
That kind of event does not happen very often in the arts.