The article is wrong. He is still Ambassador to Germany. He never gave up that position whike serving as acting DNI.
As per wiki:
Richard Allen Grenell (born September 18, 1966) is an American diplomat, civil servant, and media consultant. He currently serves as the U.S. Ambassador to Germany, and the Special Presidential Envoy for Serbia and Kosovo Peace Negotiations. Grenell briefly served as acting Director of National Intelligence in the Trump administration.
I didn’t realize that. So he could still be amb to DE while also being the acting FBI Director for 180 days!
Thanks,
Mark