And furthermore ... the Khazar Kingdom lasted only a few years.
The King and his Court converted to Judaism; the rest of the people did not.
Prior to the last few hundred years "people" subject to monarchs or warlords had no "choices" of any kind, and they were so far removed from their sovereign as to be practically non-existent.
The "people" would have been illiterate and impoverished beyond imagination.
The idea that descendants of Mongols and Tatars on the steppes of Central Asia would acquire "Hebrew as a Second Language" practically overnight, get circumcised and embrace Torah Judaism, give up their uncooked pig meat and yak milk in favor of Kosher Laws -- is so absurd that it is not even laughable.
If all Jews were from Khazaria, then where the hell did the Jewish rabbis who were summoned to the Court of the King of Khazaria come from?
Oh!
I get it! ... The Jewish rabbis all had to wait for Russia to destroy Khazaria in the 9th century, so that there would be enough Jews in the world to travel back in time in order to convert the King of the Khazars.
The only people propagating this myth and believing it are the former Nazis and modern neo-Nazis, who when not considering the Jewish people to be guilty of "Deicide", and a race of devils descended from Satan, are insisting that we are not Jews nor have we ever been descended from Jews.
And THAT, my friends, is what I call serious mental illness.