Why was Zeus portrayed as unfaithful to his wife?

Answer: Zeus was so unfaithful to his wife because when the early Greek peoples encountered other smaller groups (many of whom they absorbed) they assumed that the gods those people worshiped were the same as theirs, just with different names - so the new peoples chief god must just be Zeus by a different name and so took on their rituals and myths of that god and called them myths and rituals of Zeus.