I do not know where to start.
Renaissance was a result of centuries of development, it was not a cause of it. And where Machiavelli promotes Social Darwinism? Also are you saying that theories of Machiavelli were the cause of Renaissance?
Take the laxative and start thinking. Machiavelli described Renaissance political life of his times - which was THE survival of the fittest [rulers on that occasion]. The same thing happened in the earlier centuries, too [take his "history of Florence", for example] - but the description to be gleaned from "the Prince" is the most direct hence the best. And if Machiavelli's instructions are not Darwinistic, then what are they? Again, start thinking [after the laxative works].