Fiction: the peasants freed themselves and made Democracy. Reality: the aristocrats were underpaid and quit, giving you Democracy by default.
Here's the question: is herding peasantry inherently unprofitable? They create wealth and problems, but do their problems & upkeep always cost more than the wealth?
Possibly the accounting works out if the peasants grovel and submit efficiently enough... If they fight you on it, it's 100% not worth it, which is part of the pattern of security always being affordable. Even peasants can afford to secure themselves even against lords - they just shouldn't, because a recursion makes this security an exception. If peasants moronically secure themselves against lordship, it means the lords need to secure themselves against peasants, which typically boils down to peasant genocide. Justice always has the advantage, and under Democracy turns out the Nash equilibrium is death camps. All are equal in death; just start killin' until every Egalitarian is dead. Not really the intended result, but problem: solved. (Or maybe it is? Are the peasants mad because they ain't dead? The demands have become strident and shrill...)
P.S. Crime is always optional, because security is always affordable.