the origin of the 12 Olympian deities

If the wikipedia article (and The Oxford Handbook of Ancient Greek Religion) are to be believed the current theory is that the idea of a 'ruling council' of 12 gods is based upon Anatolian models.
Wikipedia claims (for whatever it's worth)

The Greek cult of the Twelve Olympians can be traced to 6th-century BC Athens and probably has no precedent in the Mycenaean period.

Which I read as claiming that there is no evidence of -worship/recognition in the form of religious practice- of the dodekatheon, not that they didn't posses the concept of a 'council' of 12 gods (just to clarify what I am saying by posting this quote)

A picture of two concepts (a concept of a 'class' of 'Olympian' deities, those that supplanted the titans, and the concept of 12 gods) being combined is suggested by a few pieces of information
In ancient Greek religion, the "Olympian Gods" and the "Cults of Twelve Gods" were often relatively distinct concepts - C.R. Long, The Twelve Gods of Greece and Rome
and

According to Stoll, Heinrich Wilhelm (translated by R. B. Paul) (1852). Handbook of the religion and mythology of the Greeks. Francis and John Rivington. p. 8. "The limitation of their number [of the Olympians] to twelve seems to have been a comparatively modern idea."

And another excerpt from Long. Outside of the speculation on the tomb decoration the take away is that the Hittite 12 and by extension at least some forms of the Anatolian 12 (since the passage opens by putting forward an Anatolian origin for the Etruscans) were made up of 'anonymous' gods.