‘And all the men of Shechem assembled themselves together, and all the house of Millo, and went and made Abimelech king, by the oak of the pillar that was in Shechem.'
The rivals now being satisfactorily removed, the instigators of the activity, the chief men of Shechem, assembled for a coronation at a sacred place.
“All the house of Millo”. Beth-millo means ‘the filled-up place' (compare a similar place in Jerusalem - 2 Samuel 5:9; 1 Kings 11:27; 2 Kings 12:20). This was probably the fortified tower and temple (verse 46), built on top of a previously levelled building or a filled in indentation. Thus the priests of Baal-berith were involved in the ceremony (Judges 8:33). They made Abimelech ‘king' in their own fashion, but note that even here, as regards the section of Israel over whom he ruled he was ‘made prince' (Judges 9:22). What the Shechemites saw as a king Israel saw as a prince.
“By the oak of the pillar that was in Shechem.” Compare Joshua 24:26-27. This was the place where they had originally entered into the tribal covenant. They did not want this to be seen as an attempt to break from the covenant but as in their own way a confirmation of it. Ironically this ‘standing stone' was originally intended to be the witness to them lest they denied Yahweh (Joshua 24:27 with Joshua 24:24) which was precisely what they were doing, although they may not have thought so.
It should be noted that Abimelech is not rated as a judge and that throughout the whole narrative Yahweh is not mentioned. The few references, and they are sparse, are to ‘God'. It is the disastrous tale of failed kingship, displeasing to God, a warning of what kingship involves.
There is a great indirect stress on Baalism in this section, although no direct reference to the worship of Baal (however see Judges 8:33 - but the people may well have seen themselves as worshipping Yahweh under the name of Baal-berith. God saw them as worshipping Baal). For example, the chief men are called ‘baals', those from the ‘the house of Millo', the Baal-berith temple, are involved in the coronation, Gideon is only referred to as ‘Jerubbaal', the sons are probably seen as offered as human sacrifices, bought as it were, with money from the house of Baal-berith.
But the coronation actually took place at a site seen as sacred to Yahweh. The whole incident brings out the dangers of syncretism, begun when Gideon made the ephod, and continued by his behaving like a king with multiple marriages. It was a tragedy waiting to happen.