I don't know if any edition of D&D has really done a great job plugging in character classes into the setting in some concrete way. Oh, I suppose we've had strongholds going as far back as 1st edition (maybe farther?) AD&D, think about your sociology classes and the creations of institutions. An institution isn't necessarily an organization, it's more of a "complex integrated set of social norms organized around the preservation of a basic societal value." The more common institutions include family, education, government, economy, and religion. How does a D&D character fit into these institutions? Do they?
In my experience, the answer is they usually don't. Sure, sometimes the PC is working with the government when they're clearing out a threat, but this is more akin to contract work than having any direct connection with the government. We jokingly (or not jokingly) refer to PCs as murder hobos and what's a hobo? A tramp, vagrant, transient, drifter, bum, or vagabond. These are people who don't have strong ties to any institutions and we kind of like it that way in seems. Getting PCs to respect any authority other than themselves is often like pulling teeth. One of the worst thing you can do to a PC is to rob them of their autonomy by having a social superior give them orders or for their peers (as if they have peers) to put social pressure on them. (Of course I write all this while playing in an Eberron game where we're directly tied to the government as agents of the crown, so, uh, exception to the rule?)
So I made the longwinded statements above to set this up. To understand the odds of a peasant's revolution succeeding you kind of need to understand all the players (institutions, important NPCs, organizations, etc., etc.), what their roles are, and what they want. And I feel as though most D&D adventures and settings, we really don't think about those kinds of things very much.
@doctorbadwolf is right, you could have clerics, paladins, wizards, or other PC type classes supporting the peasants for a variety of reasons. Americans in particular are rather sympathetic to rebel causes, in no small part because of our own national founding myths and history, so in most campaigns the rebels will likely be the good guys.