Google has been an ad company way before 2013.
AdWords was launched in 2000. Google bought DoubleClick in 2007. https://en.wikipedia.org/wiki/DoubleClick
Second paragraph of the Google 2004 financial report (first paragraph described what Google is):
We generate revenue by delivering relevant, cost-effective online advertising. Businesses use our AdWords program to promote their products and services with targeted advertising. In addition, the thousands of third-party web sites that comprise our Google Network use our Google AdSense program to deliver relevant ads that generate revenue and enhance the user experience.
https://www.sec.gov/Archives/edgar/data/1288776/000119312505...