This falls into where your ideology belongs to "see" what is most likely:

* Amazon paid politicians in EU to craft and pass packaging laws that they would have to enforce/abide by, but have the resources. [Who and how many is anyones guess].

* EU Politicians meaning well, created policy to clean up packing with enforcement in all EU countries, maybe hoping large companies pay for the cleanup. Unintended consequences mean small shippers have a higher burden.