Some Christians will say that God judicially hardened Pharaoh's heart as judgement on his wickedness of causing the murder of many Hebrew newborns (Exodus 1:16) and his cruelty and mistreatment of Hebrew slaves, etc. But he could have freed the Hebrew slaves had God not hardened his heart.
Since God is sovereign He can judicially harden the heart of anyone as judgement on their sins. The more biblically consistent answer is that Pharaoh's heart was already hard because of original sin. He did not have the capacity to "change his mind" about his hard heart. He could change his mind about individual choices like letting the Hebrew people go free. Therefore, as God's judgement on Pharaoh and the Egyptians He judiciously hardened Pharaoh's heart from "letting my people go" in order to make the circumstances for the Egyptians worse. Hence "God shows mercy on whom He wills and hardens whom He wills."
You would have to give some support to your argument that God gives "tacit approval to the interpretations of religious leaders," because He doesn't as the bible forbids "private interpretations" in several places, one example is 2 Peter 1:20-21. Saying that God may be a "cult leader inspiring other cult leaders to control the masses..." sounds like the type of diatribe against religion in general that I used to give when I was an unbeliever. There is no substance behind it and it is basically blaming God for the actions of men. Men are responsible for their own sinful actions, if they are following biblical principles (properly interpreted) their actions are not sinful though they will seem egregious to other people (especially non-believers.)
I'm not arguing the existence of God, just giving you the answer to a passage of Scripture you have qualms with.