It's only an inevitable outcome if you enable people to acquire enough capital to distort markets in their favor. But this is not something inherent in the notion of the free market itself - rather, it is driven by the property rights arrangement, which is actually somewhat orthogonal to free markets. Where government exists in the first place, its monopoly on violence essentially means that property rights are that which said government recognizes as such and uses force to protect, if necessary. It doesn't have to protect arbitrary accumulation of capital, though.