Slop.

Wiki page for it I think Kasparov has distanced himself from it but I've never seen him fully deny it, though nobody calls him on it. If you've heard of the 'Tartaria' or 'mud flood' theory I think they share the same conspiracy roots Mia Mulder video on Tartaria

On the creator of the theory:

He also claims that Jesus lived in the 12th century A.D. and was crucified on Joshua's Hill; that the Trojan War and the Crusades were the same historical event; and that Genghis Khan and the Mongols were actually Russians, that the lands west of the Thirteen Colonies that now constitute the American West and Middle West were a far eastern part of "Siberian-American Empire" prior to its disintegration in 1775, and many other claims that contradict conventional historiography. As well as disputing written chronologies, Fomenko also disputes scientific dating techniques such as dendrochronology and radiocarbon dating