I think you might be partially on to something here; generally the idea being that food delivery is essentially commoditized and Amazon is uniquely suited to thrive in commoditized industries with their vast infrastructural advantages.

They do have Whole Foods and Amazon Go, which both supply ready-to-eat foods along with meal kits. It would be a minor logistical challenge to simply start preparing their own meal kits on-demand and delivering them via Prime Now (which operates inside the exact same markets as Amazon Restaurants?) with the bonus benefit of owning quality control in the kitchens.