Philosophers were these somewhat smart guys, who saw the world with different eyes.
The Enlightenment was all about figuring it out and these guys were determined to, without a doubt.
From the French nobility came Montesquieu, who discovered the three branches familiar to you.
From legislative, executive and judicial, with separation of powers, his analysis was official.
Then came Voltaire, a Parisian, who fought against intolerance of religion.
He mastered deism based on reason and natural law, close to the “world machine” that Newton saw.
And of course there was Diderot.
Writing the Encyclopedia is how he is known.
It was 28 volumes of trying to change the way people think.