That's exactly what he said, that monarchism and democratic republics are equal forms of government as far as the Church is concerned.
"The most Christian King, Louis XVI, was condemned to death by an impious conspiracy and this judgement was carried out. We shall recall to you in a few words the ordering and motives of this sentence. The National Convention had no right or authority to pronounce it. In fact, after having abolished the monarchy, the best of all governments, it had transferred all the public power to the people -- the people which, guided neither by reason nor by counsels, forms just ideas on no point whatsoever; assesses few things in accord ance with the truth and evaluates a great many according to mere opinion, which is ever fickle, and ever easy to deceive and to lead into every excess, ungrateful, arrogant, and cruel..."
--Pope Pius VI, allocution of 17 July 1793, Pourquoi Notre Voix
Writing to the King of Cyprus on kingship, St. Thomas Aquinas forthrightly declared monarchy to be “the best of governments, ” a pronouncement ratified by Pope Pius VI in modern times in the allocution he delivered on the occasion of the execution of Louis XVI of France. St. Thomas says that inasmuch as “the welfare and safety of a multitude formed into a society lies in the preservation of its unity, which is called peace” and “it is manifest that what is itself one can more efficaciously bring about unity than several . . . therefore the rule of one man is more useful than the rule of many. Furthermore it is evident that several persons could by no means preserve the stability of the community if they totally disagreed. . . . So one man rules better than several who come near to being one.
“Again, whatever is in accord with nature is best, for in all things nature does what is best. Now, every natural governance is governance by one. In the multitude of bodily members there is one which is the principal mover, namely, the heart; and among the powers of the soul one power presides as chief, namely, the reason. Among bees there is one king [queen] bee and in the whole universe there is one God, Maker and Ruler of all things. And there is a reason for this. Every multitude is derived from unity. Wherefore, if artificial things are an imitation of natural things and a work of art is better according as it attains a closer likeness to what is in nature, it follows that it is best for a human multitude to be ruled by one person.” This is why God “promises to His people as a great reward that He will give them one head and that ‘one Prince will be in the midst of them’ (Ezech. 34:24; Jer. 30:21).”
St. Thomas only strengthens his case by pointing out that if, according to Aristotle, “it is the contrary of the best that is worst, it follows that tyranny is the worst kind of government. . . . For the same reason that in a just government the government is better in proportion as the ruling power is one -- thus monarchy is better than aristocracy and aristocracy better than polity -- so the contrary will be true of an unjust government, namely, that the ruling power will be more harmful in proportion as it is more unitary. . . . Danger thus lurks on every side. Either men are held by the fear of a tyrant and they miss the opportunity of having that very best government which is kingship; or they want a king and the kingly power turns into tyrannical wickedness.” To be delivered from tyrants, “the people must desist from sin, for it is by divine permission that wicked men receive power to rule as a punishment for sin.”
--Solange Strong Hertz, Democracy, Monarchy, and the Fourth Commandment