Before-and-after comparisons and other marketers' thoughts
In resume, what the community has noted and concluded with this update:
An increase in People Also Ask (PAA), a query refinement feature designed to drive users to the answers they want to see.
Scraper spam in search results.
Most of the “view full answer” links open other people’s sites in a full screen iframe
Pure spam, but loved by Google.
After the update, many sites lost positions for health and medical related queries. The reason they lost positions is because Google’s algorithm started associating medical queries with scientifically proven answers. Not that there was anything wrong with the alternative medicine sites. They just weren’t relevant to the user intent inherent in medical search queries that demand proven, non-speculative health remedies.
In many instances, Google updates change the way Google understands the meaning of queries and/or web pages (i.e., BERT). This can result in different sites moving up in rankings, sites adjusting to the algorithms’ new understanding of what a user is looking for when they make a particular search query.
Some sites may lose rankings not because they have done anything wrong, but because the algorithm’s judgment of what is relevant has changed.
In other cases, Google may introduce query refinement features, such as People Also Ask (PAA), which can move a web page down from position 2 to a virtual position 5 (although technically it is still position 2).
But People Also Ask (PAA) can also mean that another site appearing within the PAA function can gain more traffic because it is more topically relevant to the user making a particular query, gaining traffic for a query that otherwise would not have been rewarded.
Google could also introduce more FAQ-rich results that may affect the site’s visibility in search results (positively and negatively).
These are just a few examples of how factors external to a website can negatively influence rankings.
So if your site has suffered a negative change in search performance it is good practice to first look outside of your site to try to understand what may have changed and then go back to your site and see if any information can be gleaned.