The destinction is that amazon is not using it's position to enter another market, which is what this whole thing is about.

The EU argues that people use the google search function to search for items to buy (but not necessarily from google itself), google has a monopoly on search so this is a reasonable assumption.

The problem is then twofold, google shows it's own (and, argued by the EU, inferior) results above that of established competitors. And that's the rub.

Amazon does not abuse it's monopoly in the sense that people who go there explicitly go there to shop already, amazon itself is already an established seller.