Why is "Mongol invasion of Europe" trending?

Wikipedia Overview

From the 1220s to the 1240s, the Mongols conquered the Turkic states of Volga Bulgaria, Cumania and Iranian state of Alania, and various principalities in Eastern Europe. Following this, they began their invasion into Central Europe by launching a two-pronged invasion of then-fragmented Poland, culminating in the Battle of Legnica, and the Kingdom of Hungary, culminating in the Battle of Mohi. Invasions were also launched into the Caucasus against the Kingdom of Georgia, the Chechens, the Ingush, and Circassia though they failed to fully subjugate the latter. More invasions were launched in Southeast Europe against Bulgaria, Croatia, and the Latin Empire. The operations were planned by General Subutai (1175–1248) and commanded by Batu Khan and Kadan, two grandsons of Genghis Khan. Their conquests integrated much of Eastern European territory into the empire of the Golden Horde. Warring European princes realized they had to cooperate in the face of a Mongol invasion, so local wars and conflicts were suspended in parts of central Europe, only to be resumed after the Mongols had withdrawn. After the initial invasions, subsequent raids and punitive expeditions continued into the late 13th century.