No capitalism is not about decentralization.  Capitalism has a number of bad and useless definitions, useful only for its attackers who want to dominate markets themselves, but the primary essence of real capitalism is voluntary exchange with a lack of coercion.  Centralization happens everywhere, even in capitalist systems, and in the absence of state interventionism like bank bailouts, too much centralization can in fact lead to the downfall of firms which get too large and therefore too bureaucratic and inefficient.  That's what used to be called creative destruction and it was great.  Now the government just picks winners and losers.  This fear of giant monopolistic firms overrunning markets has never happened, except when the state made it happen, which is everywhere now.