This belongs in the ASB forums. Cortez did not want to be Emperor of the Triple Alliance and even if he did who would support him? Cortez's allies were other Native American tribes subject to the Aztec and resented their harsh rule, the reason why these natives allied themselves with the Spanish was because Spain promised them autonomy under their rule if they defeated the Aztecs (a promise the Spanish conveniently forgot to keep.) If Cortez somehow did become Emperor then when the Europeans comeback they will find a weak chiefdom that will be easily swept aside.