The general force behind this is the expansion of sub-same-day delivery which they have been pushing hard for the last year. Amazon fresh was a more traditional model which didn't fit in well with amazon's strengths (fulfillment, automation) because they tried to enter a market they were directly competing with (in-person shopping) and charged users for delivery in addition to their existing membership.

It's a welcome change IMO, amazon groceries are super cheap online and now delivery is free. They have been removing the fresh name from products for a few months now and replacing with amazon grocery. Certainly less confusion for consumers, at least

Related: https://www.aboutamazon.com/news/retail/amazon-same-day-fres... https://www.aboutamazon.com/news/retail/amazon-same-day-fres...