Why did Saul obey the people instead of God? Because he feared the people instead of God. He feared the human consequences of obedience more than he feared the divine consequences of sin. He feared the displeasure of the people more than the displeasure of God. And that is a great insult to God.
In fact, Isaiah says it is a kind of pride to be afraid of what man can do while we disregard the promises of God. He quotes God with this piercing question: “I, I am he that comforts you; who are you that you are afraid of man who dies, of the son of man who is made like grass, and have forgotten the LORD, your Maker?” (Isaiah 51:12–13).
Fear of man may not feel like pride, but that is what God says it is: “Who do you think you are to fear man and forget me your Maker!”
The point is this: if you fear man, you have begun to deny the holiness, the worth, of God and his Son Jesus. God is infinitely stronger. He is infinitely wiser and infinitely more full of reward and joy.
To turn from him out of fear of what man can do is to discount all that God promises to be for those who fear him. It is a great insult. And in such an insult God can take no pleasure.
On the other hand when we hear the promises and trust him with courage, fearing the reproach brought upon God by our unbelief, then he is greatly honored. And in that he has pleasure.