Amazon is the largest online marketplace in the US and arguably so in the whole world. So far so good, but that doesn't mean they don't enjoy a bit of an external traffic, who wouldn't?! Bringing them fresh leads, filtered on top of that, with some great purchasing intent. It sounds to me like a pretty enticing offer for them... and it is!
Amazon just loves external traffic - Pinterest, Facebook Youtube, Instagram - "Bring it On!" they excitedly shout at you. And the best part is - you already know how to do that, running paid ads, right? Why not throw some at the good old Amazon.
But "I don't know how exactly..." you'd say and "I don't really have the time, I'm concentrating on the main part of my business that brings the mula."