They may have been morally corrupt in private, but they ran the nation and church well. Tell that to King David. David's sin was private. God thought enough of it to send a prophet to denounce him. His private incompetence had severe repercussions for the nation.
Some moral issues are appropriately matters for the political process.
Abortion, for instance, concerns another human life. Gay rights ordinances, school prayer and pornography involve public conduct, institutions and effects. But there is no single Christian position on such issues. There's not single position on any issue. This does not stop us from establishing a moral position that's backed with civil legislative teeth.