Capturing part of the system and rent-seeking is not outside of capitalism. It's just one economic strategy among many, like war, enterprise, arbitrage, theft and swindle, etc. Capitalism has no method for preventing it because capitalism doesn't care. Capitalism is not a moral system. It's an economic system. Having any sort of morals or conscience only limits your ability to be the best capitalist you can be. There's no point preaching capitalism and then some capitalists get their hustle on and be like, Not like that, tho.