Around the time they re-corporatized into Alphabet. Probably a little while before that, so at least a solid decade since that's been completely out the window.
Also, it only ever referred to putting ads before search results... which is how it is now. They clearly dropped any principles they had a long time ago. It's honestly a little shocking more isn't written about how Google was one of the earliest to begin its enshittification process, probably with the death of Google Reader, which was the death knell for RSS feeds and the Old Internet.
They restructured as Alphabet in 2015, and Reader was shut down in 2013. Google was founded in 1998. So that means it took about 15 years all told for Google to completely shed any ethics or morals they had about being a better company. That's how quickly selling out your principles happens now.