Google has these in-depth articles for their snippets, they launched it in 2013 but now they are gone. According to Moz data they no longer show up. Also FiveBlocks who tracks data on this said they are all gone as well.

Here is a chart showing the in-depth articles going missing over the past two days in Google’s search results:

Here is the data from FiveBlocks:

Here are before and after images of the search results:

They disappeared once before in 2016 and then came back shortly after.

I am not sure if this is a bug or a change with Google.

Forum discussion at Twitter.