In a way Stalin was also a National Socialist because he advocated “Socialism in One Country”, as opposed to Lenin and Trotsky’s Internationalism. If anything, Stalin’s goals for Russia were no different than that of the Czars. He also tried to Russify the rest of the Soviet Union.
> In a way Stalin was also a National Socialist <
A nationalist puts his own country first. A socialist believes in the primacy of some collective - individual rights must give way to “the greater good”.
Those two beliefs are not mutually exclusive. You can be both a nationalist and a socialist. As you noted, Stalin is one example of that. Hitler is another.