Morrison and Volker were temporary Trump employees...
The rest of the witnesses have admitted the investigation into Burisma stopped and never started again when Biden fired that prosecutor...They all feared Guiliani/Trump digging in to Burisma and especially the events of 2016 suggesting that he was a back channel that was going to harm National Security when in fact Rudy is uncovering the corruption not only in Ukraine but the American apparatus that enabled it...
Apparently the entire foreign service leadership in Ukraine is corrupt and trying to cover for Obama/Clinton while fomenting their own agenda as it deals with Ukraine...I suspect they were all highly disappointed/scared when the new President won the election...
I have a solution - FIRE every one of them. Why on earth in the electronic age do we have huge embassy and consular offices in every country on earth? This is a tip to bygones, like a city still employing streetlamp lighters. Too often these striped pants foreign service types end up advocating the interests of the country to which they are posted and NOT those of America. Cut the State Department, CIA and NSC in half and post most of the rest of them around the country.