"People want to spend money and they are desperate for places to do it."

I dont think people are desperate to spend money.

Your dad likely had a upturn in customers due to mass demand for personal fitness devices.

Due to social distancing, gym closures, anything fitness related for home/personal use is selling out.

When covid-19 lockdowns loosened, I expect downturns in these areas.

The market will be flooded with people trying to do returns and reselling the equipment.