Tartary appears to have been written out of history because it was an example of a successful nation without a central government. Rather it seems to have contained a number of self governed nomadic tribes, with a "great king" who would officiate disputes between tribes.
Historians today will claim that it was never a real nation, and that records predating 1911 which refer to it as a proper country were erroneous. Entries on Tartary can be found in earlier editions of the Encyclopedia Britannica.