“ it went back to Denmark”
By magic?
From Wikipedia.
https://en.m.wikipedia.org/wiki/Greenland_in_World_War_II
On 5 May 1945, Greenlanders celebrated the liberation of Denmark in Nuuk.[19] The Greenland Administration under Eske Brun surrendered its emergency powers and again came under direct control from Copenhagen. Kauffmann returned to Copenhagen, where treason charges against him were dropped, and the Danish parliament ratified his agreement with the United States. The United States presence continued in decreasing numbers until the Kauffmann-Hull agreement was replaced by a new base treaty in 1951.[20][page needed] The American presence brought Sears catalogs, with which Greenlanders and Danes ordered modern appliances and other products by mail.[21] The successful experience of an independent Greenland led to a dramatic restructuring and modernization of Danish policy with respect to the colony.
https://en.m.wikipedia.org/wiki/Proposed_United_States_acquisition_of_Greenland
] In April 1951 Denmark and the United States signed the Greenland Defense Agreement. Replacing the 1941 agreement, it allows the latter country to keep its military bases in Greenland, and to establish new bases or “defense areas” if deemed necessary by NATO. The American military can freely use and move between these defense areas, but cannot infringe upon Danish sovereignty in Greenland. The agreement remains in force as long as the NATO treaty does.[123][124]