After the fall of Mycenae in 1200 B.C, Greece sank into a period of decline commonly known as the Dark Ages, which lasted until approximately 800 B.C. During that time, Greece became separated from the Orient and collapsed into itself. Writing ceased as a sub-Mycenaean culture tried unsuccessfully to carry on what had come before. Most of what we know of the first half of the dark ages is told through items buried with the dead and remnants of pottery. The second half saw a reawakening of the Greek spirit and an evolving political system leading to the Polis as the ultimate end point.
With the death of the Mycenaean kings, the notion of hereditary royalty was erased. In its place rose the Basileus as a new kind of leader. He could never be a king because the king’s powers had been dispersed among the people. Priests served the role as spiritual advisors and the common people organized themselves in assemblies to handle local administration. The Basileus was left with (or took) the role of war leader and successor to the war leaders of the invaders from the north who combined with elements of local government. He was only able to dominate a small area – a single village and its environs because he did not possess the power to control more. Consequently, his war leading ability was confined to raids on other villages.
The Basileis were not wealthy and lived by agriculture – on their own land and the land assigned to them by the community. Their possessions were mainly treasures, food, and metals as described in the Iliad. They did not have a higher standing than their fellow tribesmen economically, politically, or by their customs which basically mirrored those of the wealthy. The reputation of any one of them depended on their own prowess -- the ability to be a military leader. Some locales had more than one Basileus working together as in Elis as described in the Odyssey.
The Basileus was absolutely fundamental to the development of the Polis because without him there would have been no unified structure to serve as its foundation. In the late dark age period, the Greeks could have gone in either of two directions politically: strengthen collective action through a complex political organization or move toward personal leadership. There is evidence that the latter was attempted; that the Basileus became more powerful for a time. But that path was a dead end and he was eventually replaced by an administrator type – like the Archons of Athens. He lacked the historical requirements for personal leadership – wealth, a significant following among the people, and precedent. Ultimately, the people were unwilling to cede power to the Basileus and turn him into a king. They kept the power for themselves and elected administrators who they felt they could control.