Reddit has basically gone from a democracy to a dictatorship. If mods don’t obey they’re replaced until reddit finds someone who falls in line.
The most senior of the remaining mods in there then became the top mod (note that it is ordered by activity in that graphic not seniority).
In what may appear to be a surprising coincidence, this is the same sub and it was three years ago that the current aggrieved mod got the top mod position by having others removed.