Not really surprised
The problem with Chef was and is (AFAIK) that integration into 3rd-party things was always quite complicated.
This is maybe rooted in the idea that chef would be *the* source of truth of an enterprise and not some cog-in-the-wheel.
You can see this when you look how e.g. The Foreman tries to integrate chef in comparison to ansible.
I have done some chef in the past (now everything is ansible) and the learning-curve was comparatively steep.
So, chef's "mind-share" was certainly shrinking.
If you do some google-searches, you also get to postings on reddit where people claim that large chef-environments claim that they became unmanageable over time...
Chef's hosted chef-server (which we never used) was also often criticized for having less-than-stellar availability-figures.
Some aspects of chef I really liked, e.g. the fact that it ran continuously and thus there was little doubt about the state of the node.