Google violates a very clear concept in antitrust law known as tying or bundling: Forcing a manufacturer to install x and y apps in order to get the z app that they actually want. Apple is installing their own apps on their own phones, and therefore, cannot be violating the law in the same way.

The fact that Google forces manufacturers into this arrangement is exactly what makes it illegal. If Google was just selling Pixel phones with Google software, nobody would bat an eye.