The notable CEO resignation / sudden "retirement" list keeps growing since September 1, 2017. Some industrious and diligent beaver has taken to putting it all down and updating it daily. Ooh ahr.
783 names and counting as of this writing. It includes judges, politicians and other senior public servants beyond just CEOs and other similar C-suite executives and company directors.
The whole list is here at Google Docs - Notable Resignations
Surely unprecedented, but it must be all just purely "coink-e-dink" mis amigos. Nothing to see here ...move along.