It’s not so much that Genghis Khan directly impregnated a huge number of women, but rather that his sons and grandsons were themselves high-rank men who impregnated a lot of women.
The emperor who has a hundred sons but has them all kill each other like the Turks did competing for the caliphate doesn’t spread the DNA.
These dynastic guys clearly made sure a number of sons were chiefs, mayors, some such local leader where he was a local alpha male and thus had lots of sons, too.