The theory is roughly that before the Black Plague, the population was stuck in Malthusian dynamics at the top of the logistic curve - population had expanded to the level that land could support.

The massive deaths allowed the remaining population to only farm the most productive land, leading to a massive surplus. The elite were able to capture that surplus and fund things like art, science, etc. Some of those scientists were able to create technology that led to further efficiency gains, so that technology could make the economy grow faster than population growth could catch up.

There are a ton of things that allowed that surplus to translate into technology and economic growth. But AFAIK the leading theory is that without the massive shock from population decline due to the bubonic plague, that surplus would have never existed to begin with, so how it was allocated would have been moot.