Why are there more producers than primary consumers and primary consumers than higher order consumers?

This is because the level of energy decreases throughout the food pyramid.

At the beginning with producers, they contain the most energy or 100%. However, once they are consumed, the consumer loses 90% of the energy. Thus, primary consumers only get 10% of the energy, secondary consumers only get 1% and so on and so forth higher.

Because of the lack of energy being passed along within the food pyramid, higher order consumers (typically carnivores) must have a lot of prey to consume, but this also means competition. Therefore, higher in the ranks, there is more competition which leads to smaller populations.

Hope this helps!