I'd imagine politics to play a part, both Egyptian and American. Here, the MuslimBro'hood in power, will push the gears to empty the museum and send back artifacts for it's destruction. Egyptians like Americans, do not think with one mind. Egyptian curators across Egypt will make known their preferences for Americans to hold onto anything Egyptian until such time, even if never, the MB tornado blows thru their country; while Egyptian "leaders" lobby along with American "leaders" otherwise.
The Brooklyn Museum had the finest Egyptology collection in the U.S. prior to the Met getting the huge transfer from the Government of Egypt. The reason for the selection of the Met is obvious, the Met is easy to get to, is in a very tony neighborhood and has millions of visitors each year. The Brooklyn Museum started their collection in the 19th Century, piece by piece, but they are located in a dumpy neighborhood, are next to impossible to access by car and outside of Egyptology, don’t have much to recommend them.
You are correct, the transfer was politically motivated, at at time when Egypt was doing fence mending with the West. Dam shame to see all that stuff fall into the hands of cultural Nazis.