As human beings, we are subject to changes of mood and personality. A person may behave in a kind and loving way one day, and then be selfish and surly the next.
Some people over the centuries have taken this concept and applied it to God. Certainly, they say, God can be just, and the Old Testament is right to say that God is just. But God can also be selfish and capricious, so the ancient Greeks were right to believe in a Zeus who punished men for trivialities and cheated on his wife. The Jews and the Greeks were both right. They each saw a different aspect to God’s personality, that’s all.
