From looking at "About FANDOM" in the Internet Archive, it looks like in early May 2018 Craig Palmer got fired.
- About FANDOM from May 3, 2018 - Craig Palmer listed as CEO
- About FANDOM from May 4, 2018 - Andy Doyle listed as Interim CEO
I could find no news on Google about this changeover, but it seemed to coincide with a round of investment by TPG Capital... which makes it sound more like a takeover, since Andy Doyle works for TPG Capital.