Hazaras are the descendants of local women raped by Genghis Khan's soldiers at Bamiyan.
That's too simple. Genetics proved that Hazaras have also Mongol ancestry on their mtDNA
Genetically, the Hazara are primarily eastern Eurasian with western Eurasian genetic mixtures.[39][40][41] While it has been found that "at least third to half of their chromosomes are of East Asian origin, PCA places them between East Asia and Caucasus/Middle East/Europe clusters".[42] Genetic research suggests that the Hazaras of Afghanistan cluster closely with the Uzbek population of the country, while both groups are at a notable distance from Afghanistan's Tajik and Pashtunpopulations.[42] There is evidence of both a patrimonial and maternal relation to Mongol peoples of Mongolia.[43][44] Mongol male and female ancestry is supported by studies in genetic genealogy as well, which have identified a particular lineage of the Y‑chromosome characteristic of people of Mongolian descent ("the Y-chromosome of Genghis Khan").[39] This chromosome is virtually absent outside the limits of the Mongol Empire except among the Hazara, where it reaches its highest frequency anywhere. These results indicate that the Hazara are also characterized by very high frequencies of eastern Eurasian mtDNAs at 35%, which are virtually absent from bordering populations, suggesting that the male descendants of Genghis Khan, or other Mongols, were accompanied by women of East Asian ancestry.[45]