So your argument would be stronger if you cited examples. I assume since you aren't you're arguing from a strictly theoretical / academic sense. If we're going to go that route:

  1) A monopoly can only be held accountable by the government.

This is not true. A monopoly can also be held accountable by the shareholders. A monopoly can also be held accountable by the market. Ask any cable company, for example. A monopoly can also be held accountable by new entrants to the market, ask any ISP that refuses to run lines to rural areas.

  2) The government can only be held accountable by the people.

From a strictly academic sense, this is true, but requires an election to achieve, and I've already gone over how those are captured by the very corporations governments are supposed to hold accountable. 88% of the population supports medical marijuana legalization, but it's still illegal at the federal level. Where's the government accountability there?

https://www.pewresearch.org/fact-tank/2022/11/22/americans-o...