Google Shopping, Google's platform where customers view sponsored product listings (often when they search for something like "buy wireless headphones" on Google), is no longer where Amazon advertises.
For many years, Amazon spent a lot of money to display its product advertisements there, which helped direct Google searchers to Amazon's website and increase sales.
Why does this matter so much?
It eliminates chronic reliance.
One of the biggest advertisers on Google Shopping was Amazon. Google allowed it to reach customers directly when they were looking to make a purchase. Pulling out of that is a premeditated, unexpected move, similar to Starbucks' decision to quit selling coffee in airports.