There were roughly 100x as many Europeans as Mongolians in the 13th century
Well by the time their armies arrived in Europe 'true' Mongols were a minority. Just like the Huns and other stepped empires they included many Turkish, Cuman, Finno-Ugric and other nomadic tribes.
Conquering they much territory is an extremely unusual event
Steppe empires weren't that rare though we just don't have that much information on those preceding the Mongols. Obviously they were much more successful than their predecessors but not necessarily that exceptional.
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Well by the time their armies arrived in Europe 'true' Mongols were a minority. Just like the Huns and other stepped empires they included many Turkish, Cuman, Finno-Ugric and other nomadic tribes.
Steppe empires weren't that rare though we just don't have that much information on those preceding the Mongols. Obviously they were much more successful than their predecessors but not necessarily that exceptional.