Google said it was an issue with indexing that caused Monday's really weird search results.
August 11, 2020 at 11:52 am
Google has now explained the massive search bug from yesterday was related to an issue with its indexing systems.
Google wrote, “On Monday we detected an issue with our indexing systems that affected Google search results. Once the issue was identified, it was promptly fixed by our Site Reliability Engineers and by now it has been mitigated.”
More information. You can learn more about this issue and the impact on sites in our story from this morning.
Postscript. Many, including myself, were not too happy with the short explanation from Google. Gary Illyes from Google tweeted additional information about why the indexing system is vital to how search results show up: