They have no transferable skills for private sector work....except maybe McDonalds. McDiplomats manning the fryers.
McDonalds wouldn’t want such a bunch of lazy time-serving layabouts....
In the old days they could be lobbyists and facilitators for US companies trying to do business overseas...and for foreign companies trying to do business in the US.
The whole system was set up so Bush I diplomats would go to private practice under Clinton. Then Clinton diplomats would go to private practice under Bush II and the Bush I diplomats would go back to work for Bush II. Then the same with Obama.
The bi-partisan combine had a well understood game of rigged musical chairs.