Profane kingship is inherently weak, thus always defensive and in fight mode, and so tyrannical. For, a sovereign who rules merely by force of arms, and not by any authority grounded ultimately in the moral lógos of things, is naturally resented by all his subjects, as being nowise legitimate under heaven (unless he be also a good master – but as purely profane it is hard to be good) and his reign is rendered thereby inherently unstable, and vulnerable.
A merely profane king cannot possibly motivate his subjects to any voluntary sacrifice on behalf of the nation; because he does not himself embody the national spirit, and cannot speak for her as her angel. He can speak only for himself. All he can do then is oppress them in his own interests, to which he cannot but hold theirs as subservient; as therefore their more or less alienate enemy.
So must a truly just and truly noble and thus truly efficacious king be also himself an anointed officer of the Church. As even her national head, he must be still subject in all things to her discipline, as must he also and likewise be vassal pledged to her high heavenly King.
The only true and truly efficacious kingship is sacred; is such then as participates divinity. Merely secular rulers are no more than bosses.