Part of it is to control yes, because God is the King of mankind and all lands on earth, whether people think otherwise or not.Sounds like the idea is more about controlling people than a concern for truth
I'm not scared, there is no reason for me to fear God
Who does such an idea benefit? Quite clearly certain religious authorities. I rest my case.
However, another part is to save us from his wrath and retributive justice. Quran is a healing. People are quite insane to chase petty things instead of craving God. They don't harm God, but God creates with truth, and they become overwhelmingly evil and lost.
When a soul is bold and does not fear God, the Quran acknowledges that warning them won't make them believe.
The ball is in their court, and God does not change what is in a people until they change what is in themselves.
Fearing God is humbly acknowledging justice. That's all it comes down to. Examination of justice will make us fear God.
People project their caprice unto God - calling him a monster if he punishes them. They think God has to accept who they have chosen to be.
It's us who have to accept God not the other way.