The problem is all large organizations strive for power. One can be more easily changed than the other, at least in democratic republics. Corporations are more like autocracies, their leadership can't be changed. One can say that corporations derive power from customers, but this is not necessarily so. As they grow larger, they can necessarily control user habits through psychological means. The government can too but it has a lesser incentive, as power is more distributed, again in a democratic republic. Money however is a much better fitness function than power, as it can be quantified, so it is unsurprising that corporations gain power.