Early Ozeki puzzle?

[Jan de Veen <chijanofuji@planet.nl>]

After Tochiazuma was promoted to the rank of Ozeki I had a closer look 
at the historic Ozeki by means of the Makuuchi banzuke list at
http://www.banzuke.com/banzuke/BanzukeIndex.html
and the Makuuchi list at Yubiquitoyama's site: 
http://w1.858.telia.com/~u85811046/

What puzzled me most was that quite a high number of the early Ozeki 
(18th and early 19th century) only held the rank for one basho and 
(stranger still) that the majority of those were only ranked in Makuuchi 
for that one basho!

Can anyone explain this?

-- 

Greetings from a Sumo fan from the Netherlands,

Jan "Chijanofuji" de Veen

The Sumo Colosseum - http://www.geocities.com/Colosseum/6136/