Why did the children of Israel bow their heads and worship?
The children of Israel bowed their heads and worshiped because they believed the signs they saw and because they heard that the Lord had visited them and had looked upon their affliction. The signs and the report of God's visitation and care moved them to worship.
Les explains that the people saw the signs in the sight of the children of Israel and believed because they saw those signs. They also heard that the Lord had visited the children of Israel and had looked upon their affliction. In response to that evidence and news, they bowed their heads and worshiped. This occurred before Moses and Aaron went in to Pharaoh to demand that Israel be allowed to go into the wilderness to hold a feast to the Lord.
And the people believed: and when they heard that the LORD had visited the children of Israel, and that he had looked upon their affliction, then they bowed their heads and worshipped.