A Christian monarch is one who rules as a servant of God - and on the assumption that he or she was chosen by God for the job, and is guided by God in this task.
This is only possible in and for a society which is, overall, Christian - and therefore wants to be ruled by a monarch who at least aims-to rule the society on Christain principles; wants to be ruled by a monarch who himself aspires to be representative of God's will on earth and in mortal life (as best as possible with imperfect people in an imperfect world).
Anybody who is elected owes their position to the electors - or more often to those who rig and fix the election - and not to God. The exception is when the electors are few enough to gather in a room, and devout enough to subordinate their wishes to what they perceive of the divine will; and devoted enough to their people to seek a good and universal Father (or Mother) to the nation.
But for the decision of such a small group of devout people to be accepted and binding; requires that the powers of the population-at-large acknowledge the authority of this group - and this can only happen on the basis of a geniune and shared religion.
The first conclusion is that good government is not possible in the West today, because the people have no religion and are secular rejectors. It is absurd to suppose that a Christian monarch could be planted atop our society, and allowed to rule impartially and lovingly - yet with power and authority - on behalf of God.
A society has to deserve a great leader, or else the leader will either not lead, or not be great.
So there is no possible system by which The West as it is could have good political leadership.
A good leader is usually Father to the nation - but our nations are in permanent rebellion against parents, and especially Fathers. A good leader operates on the basis of broadly-shared transcendental ideals - but The West does not believe in the reality of the transcendental.
A good leader rules for the general and long-term spiritual good of his people (his 'children') - but we want only material good, and specifically for ourselves, and we want it now.
The West must first become religious, specifically Christian - and only then will good leadership become possible. And if, as seems likely, we do not become Christian; then we might as well forget about pining for good leadership - which is an irresponsible waste of our finite time; and instead concentrate our efforts and attentions on something attainable.