The concept of separating church and state is to protect both of them from each other. Once you merge the two, the state is subjected to a one party morality that hurts everyone. The church becomes subject to the laws of the state in a way that binds it to government processes and takes away its autonomy, essentially capturing it by the politicians.

Don’t merge the two, it’s better for everyone. Unfortunately, those that control the church do so because they want power and they’ll gladly leverage their cults to try to give them the power of the state.