Nothing out of the ordinary for individual government departments to turn to private contractors when the GSA doesn't offer them a service they need when they need it.
GSA has since developed login.gov, but there hasn't been a mandate that other agencies have to use it over third-parties.
There was another one (census, maybe? can't recall which agency it was) using a .gd for a while, too... don't see it on the list anymore. Not sure who signed off on putting government services behind the "control" of a country we've invaded before.