it occurs to me that a large portion of people being asked to resign are good people and it's being done for optics - if he only fired bad actors the bad guys could tie it all in to a political bias through the media as they would go with every firing and highlight it - but by ousting allies the media defuses itself on that potential narrative and preserves the ability to fire the corrupt people in droves
it was just the latest in a giant string of firings tho - this one is from over a year ago from a cursory search
https://www.npr.org/2018/03/19/594164065/trump-cabinet-turnover-sets-record-going-back-100-years