> That is their business: they sell their ability to know everything about you to anyone willing to pay for that information.
Google has information about you. Incredibly detailed, intimate information about you. Harvested by collecting and correlating all of your usage of their products and services.
Anyone can pay Google to use that knowledge in pursuit of other services, like targeted ads. No, you do not get access to that knowledge directly, but Google has it and is using it when paid to do so.
In effect, you can pay Google to have indirect use of that knowledge.