To Nietzsche, Caesar was an example of the "Highest Human Being". [Nietzsche, WM 544].
So in this polarity Christ is the lowest human being.

And yet both Christ and Caesar were conquerors in their own spheres. The Emperor Julian [called the Apostate], who tried to turn Rome back to paganism, said on his deathbed that the Galilean Jesus had conquered. He knew that the Empire would never again be pagan. This struggle between Christianity and Paganism is put in a formula by Nietzsche;
"Dionysos versus the Crucified" [WM 1052] ,and;
"We believe in Olympus--and NOT in the Crucified". [WM 1034].

But I suspect that this war is an Eternal one. An ascending spirit recognises not only that Caesar/Dionysos must have victory over Christ Soul/Crucified, but that the enemy is necessary and part of the economy of the whole.
No Christ, no Caesar; No Caesar, no Christ.

My contention is that Spengler's Caesarism ignores the necessity of a Christ Soul.

George Bernard Shaw's analysis of Caesarism naturally equated it to the Fascism of the 1930's;
"There is nothing new in Fascism...,Caesar, Cromwell, Napoleon, and his nephew Louis Napoleon are the bygone Fascist Leaders we talk most about; but they are only four out of innumerable able adventurers who have headed lawless revolts called 'coups d'etat' ', against governmental machinery that will not work fast enough to keep up with its ". [Shaw,'The Intelligent Woman's Guide', 1937]

We see here immediately that Shaw is right, but not profound enough to see that Julius Caesar's achievement was unique. His conquest of Gaul, brilliant in itself, created Western Europe as a world-historical force.

Could it be that Caesar alone had mastered his Christ Soul, and had therefore gone beyond mere 'Caesarism'. Do we have in Nietzsche's formulation the key which unlocks those great cultivators, of which Caesar is the exemplar?

I think we do.

Shaw puts his finger on the problem of Caesarism/Fascism;
"The catch in it is that Fascist geniuses are not immortal, and, as happened to the Napoleons, may wear out before they die. If they leave Fascism in incapable or vicious hands, it may produce results which are at best deplorable and at worst diabolical". [ib.]

This is what Nietzsche meant by the alarmingly chance nature of greatness. The project is to cultivate the great cultivators. To make greatness a product of Will.
To be able to make certain that a Caesar will rule, and be followed by an unbroken succession of Caesars; this is the thrust of this philosophy.So, the Caesar must first of cultivate his Christ Soul; that is imperative.

New Worlds beckon.