> How do governments become corrupt in the first place though, if they don't start that way?

I think the US government did start that way. Maybe not "corrupt" as such, but the United States was founded by plutocrats and was clearly designed to protect the minority of plutocrats against mass democracy.

> Even the log cabin has downsides compared to the nomadic hunter-gatherer lifestyle.

Yes, but I'd say the nomadic hunter-gatherer lifestyle has even greater downsides, and our current state of convenience is in many ways a vast improvement over the precarious existence of our distant ancestors.