Why we know very little about Minoan rulers and why there are seemingly few depictions of Minoan rulers in Minoan art are really separate questions, both of which I will try to get into.

Firstly, it is not entirely true that there is “practically no mention or depiction of rulers from the Minoan age at all” beyond King Minos. However, it is true that academics do face a major problem when studying the Minoan civilisation. This is due in no small part to the fact that we are yet to understand the Minoan language (or languages) as were recorded on numerous Cretan Hieroglyphic and Linear A tablets that archaeologists have uncovered. By comparison, the deciphering of Egyptian, Mycenaean and Akkadian (the political lingua franca of the Bronze Age Near East), has provided us with a wealth of knowledge about these societies. As a result, we do not properly understand any of the information the Minoans may have written about themselves. This extends not just to the history of their rulers, but even to what they called their island; the Egyptians knew the island as Keftiu, the Mesopotamians and Canaanites as Caphtor or Kaptaru and the later Greeks referred to it as Crete (Cline, 2014). While the similar sounds suggest that the Minoan name was similar to these, we simply do not know what they called the island.

That said it is not true that we know nothing of the Minoan rulers beyond the mythological Minos. While our information on the lives of their rulers, their names and the dynasties that may have once ruled Minoan Crete is lacking, there is still some things we can infer about the Minoan rulers of the Bronze Age. We know for instance, from deciphered Akkadian and Egyptian texts, that their rulers were considered a significant power and trade partner at their height. Egyptian inscriptions mention a delegation of the “Keftiu chiefs” as reported to have visited Egypt and there is evidence of significant trading and exchanging of gifts between the rulers of Egypt, the Near East and Crete based on Akkadian translations. Crete seems to have once been seen as an important trade power and there are multiple Egyptian references to “Keftiu-ships”, perhaps suggesting they were a significant naval power (Cline, 2014). While all claims made by Thucydides (and his contemporaries) on the Minoans should be treated with plenty of scepticism, that there seems to have been a myth of Crete once being a significant naval power could be seen as supporting this interpretation, even if the specific details of the story can be regarded as myth (Thucydides 1.4). In any case, it is not true that we have no mention of their rulers, just that what we do have is frustratingly sparse.

As you mentioned, the Minoan material culture can provide some evidence as to how Minoan rulers may have lived. Archaeological excavations have also found evidence of destructions that may suggest power struggles among leaders occurring in their society (Nowick, 2000).

In regards to your second point on Minoan art, there are a number of plausible reasons why the art of the Minoans might not depict, or seem to depict, Minoan rulers. Firstly, we have no way of knowing if the people depicted in various frescoes are meant to be representations of actual people or broader Minoan practices. While this is mere speculation, it is not impossible that some of the people depicted in these frescoes are indeed important members of Minoan society. Secondly, it is very important to keep in mind that the art we have today, be that frescoes, statues or pottery, must represent only a fraction of what once existed. It is therefore plausible that the Minoans were not a unique society in there apparent lack of depiction of their rulers, as opposed to say Egypt or the Near East, just that this may represent either what has survived or been found. Lastly, it may simply been down to artistic tendencies at the time. I encourage you to find a book on Minoan art. You will see that much of their art seems to depict rituals, ceremonies, activities and/or festivals (notable examples being dancers, Bull Leaping and Boxing), as well as images of nature. It may be perhaps this was what they simply preferred to depict from a religious and/or aesthetic perspective, rather than showing the rulers, and that this was popular with the wealthy who commissioned it. Furthermore, there could be symbolism behind this imagery, in particular the rituals and festivals, which we today do not understand, but at the time may have in some way been reflective of the rulers of Crete. In short, until we can decipher the Minoan language, there will be a lot we do not know about their rulers and it is not clear based on our current knowledge that any such trait of not depicting them actually existed.

Key Sources: Eric H. Cline, 1177 B.C.: The Year Civilization Collapsed, 2014 Thucydides, The Peloponnesian War Nowicki, Defensible Sites in Crete, 2000 Davaras, The Palace of Knossos, 1990