Commodore in WW2 was a Navy rank just above Captain (a one-star admiral), and at various other times was a title given to a senior Captain who commanded a small group of ships. ...
Your comment is a bit ambiguous as written.
A naval Captain is not a one star admiral. Admirals are flag officers, Individuals with the rank of Captain are not. Ships carrying flag officers fly an ensign (flag) with the a number of stars appropriate for the rating of the officer, hence the term 'flag officer'. The appropriate insignia for a Captain is a gold colored Eagle (in the u.s.) and he wears four stripes on his sleeve.
Commodore is the lowest grade of flag officer recognized in the u.s. fleets. The appropriate insignia for a Commodore is a single star. This is in contrast to Rear Admiral (two stars), Vice Admiral (three stars), Admiral (four stars), and Admiral of the Fleet (five star).
Commodore, like the 5 star rating Admiral of the Fleet, is not normally used by the services, although at various times the rating has been activated. It remains available as a 'brevet rank'. Brevet ranks are temporarily assigned to ensure a specific order of seniority during an assigned task or mission. As with your comment one example would be a small flotilla with the highest ranking officers being Captains, one of these (usually the most senior) may be breveted to Commodore for the duration of that mission. This is most likely during a time of combat when maintaining a clear line of command is deemed a critical aspect of fleet management. Ranks held as breveted are always only temporary unless later confirmed as a permanent increase in rank.
Additionally, and in the case of hubbard more accurately, yacht clubs frequently style their president or other leading individual as a
Commodore. Of course this has no legal standing whatsoever; it is only an honorific title for what is essentially the head of the organizing committee of a social group. As Hubbard registered and ran the SO fleet as his personal
private yachts, it was not wholly inappropriate that he should choose to refer to himself as the
Commodore. However, Hubbard being Hubbard and compelled to exult and glorify his position to others, extended the significance of that usage among his followers far beyond any reasonable interpretation of the term, confusing the usage and implying that the reference meant something greater than it did.
So, despite the fevered imagination & longings of hubbard and his loyalists, rather than likening the SO to some sort of naval organization it is more accurate to think of it in terms of a rather strange
yacht club, and one with very peculiar terms of membership.
Mark A. Baker