Ent believes the word you seek is "autocracy," as "aocracy" isn't to be found.
That said,
Sauron's government methods could certainly qualify as an Autocracy once
Melkor was gone, though we know some of the 'bands of
orcs', for example, had their own local chieftains, etc., which does mean a certain level of distributive power - though in the end, they did report to Sauron, we suppose, for what they did. It's a bit speculative.
Ent does not believe it qualifies as a theocratic despotism. Such would require Sauron's acknowledgement of some other Theos = or '
god figure' - of whom he was the absolute representative. Neither Melkor/
Morgoth nor Sauron seems to have acknowledged faith or belief in any 'god-figure' other than themselves and their own powers and abilities.
Melkor is the initial example of putting 'faith in self' over 'faith in
Eru' - wanting to become god of the new creation, Ea. - rejecting Eru's themes and 'godhood' in favor of himself and his own power.
Sauron overthrew his original allegiance to follow Melkor, first putting his faith in Melkor rather than Eru; then, when Melkor failed, Sauron chose badly again and put his faith in himself. During the time Melkor existed, and Sauron was his vassal, it MAY be said those whom he controlled were under a certain theocratic rule - but once Melkor was no more, and Sauron put faith in himself alone, it became an autocracy.
Both were ultimately left with only the Providence available to those who overthrew their faith in the Creator and chose faith in themselves.
Faith, Choice, and the resulting Providence are 3 of
Tolkien's pinnacle "moral and religious elements" in all his work.
Ent is working up an article now for submission for publication - a follow-up to one co-authored and just accepted for publication.
This new one's current title is
Tolkien's Silmarils: Faith, Choice and Providence. He hopes to have it submitted soon
.