Large companies resemble governments in some ways since they have people not directly connected to 'market validation' mechanism: administrators, bureaucrats, people dedicated to keeping thing going etc. Internally, the larger a company is, the more it begins to look state-like and socialistic.
Corporations themselves are also in practice intimately intertwined with government. They depend directly or indirectly on procurement, but also the legal system. The more complex regulations, the bigger the economy of scales a corporation can use. There are also specific laws that make competition illegal in some fields like telcos and friendly tax regimes for big players only.
You may note corporations are the biggest defenders of free markets when it suits them, then quickly turn the page when they require some special subsidies, bail-outs or laws to hobble their competition.