How does this square with starches occupying the bottom of the pyramid?

The short version, if I recall correctly, is that starchy foods were seen as the least bad option: fats are more calorie-dense than carbohydrates, and meat and eggs were being discouraged for other reasons. I'm not sure why starchy foods were being recommended over fruits and vegetables, which are strictly better by the same standards, but the simplest answer is probably that they were already dietary staples and the people designing the guide wanted to rock the boat as little as possible.

It's also worth mentioning that the food pyramid, and other nutritional advice contemporary with it, wasn't exclusively aimed at obesity (which at the time was rising, but wasn't anywhere close to the public health issue it is now). Managing cholesterol was hugely trendy in the Eighties, for example.

Not to get too apologetic for the advice of that era, which I view as ineffective at best. But it wasn't that inconsistent.