Actually it seems you may have made some mistakes in researching causes of viruses. Viruses have infected Windows machines more in the past as it is a larger target, there are far far more Windows users than Apple and Linux users by a large large margin which means you have a higher target for your attack. MacOS makes up about 7% of the operating system market at its peak and Linux hovers are 2-3% so planning a virus to affect one is not a great idea unless… Microsoft’s security started to become so strong that malware developers now have to seek the open vulnerabilities (see op). Since that’s not understood we can move on
As far as the article indicates the ad itself was not actually a Google fault whatsoever, it actually appears as a Google ad though. The malware itself is installed by other means entirely but the user themselves, the relation to Google here is that the malware already installed on the machine disguises itself as a Google ad. Really, honestly, read the article next time. This is 100% standard malware attack on an unprotected system.