The 2nd Amendment was introduced because the states were afraid a standing national army would give too much power to the Federal government, so the plan was to have individual states field their own militias instead. Also because the principles of the right to self defense were established in British common law at the time - but that has more to do with keeping cougars and vandals away than any abstract fears of tyranny.
You're right that it didn't really protect "peasants" - it mostly protected the interests of rich landowners. Which is, ironically, what Ben Franklin was actually arguing against with his often repeated (and misinterpreted) quote about those who trade a little liberty for safety deserving neither.
He said stuff like that left and right. He was very much in favor of sticking to one's ideological guns even when personally inconvenient. He was arguing in favor of the federal government retaining the authority to tax in the instance everyone quotes.
The idea that the 2nd amendment protects the peasants is also wrong and it's one of the reasons people laugh at USA, when the 2nd amendment was approved, Grand Duchy of Tuscany had already abolished death penalty.
2nd amendment was introduced to permit people to shoot tax collectors (i.e. the British)