This is about inventory and personalization. Today, General Mills pays a lot to have a box of Cheerios placed on set, and more if the actors interact with it (eat the cereal, for example). But as much as they pay, it’s a fraction of what that ad revenue could be.

ELI5: Imagine if the box of cereal was entirely green, like a green screen. Now every cereal maker has a shot at product placement. Amazon can rotate the advertisers on different streams, or by region. It becomes more lucrative in international markets where there are regional cereal manufacturers that would want to get in on the action.

Ultimately Amazon makes a lot more money, and presumably the audience sees ads more relevant and personalized. Amazon knows I’m in my mid forties, so they’d probably show me Special K instead of Cheerios…

Creepy, yes. Also very profitable.