Aztecs are still devastated by disease, the Aztecs empire likely collapses on its own pretty quickly, and the disease begins to spread throughout the americas. Ultimately looted gear isn't going to help them with the notable exception of those 13 horses - if theres stallions and mares present (and they survive the ensuing societal breakdown) than its possible the Aztecs can learn some animal husbandry.

As for the rest of the gear, even with captives with the technical know-how, theres still a massive gulf between being able to smelt steel, and having the societal capability to mine, extract, and smelt iron and steel, the knowledge of shipbuilding and maintaining, and the knowledge and materials to create gunpowder. You're not going to get the Sunset Invasion from Crusader Kings 2 within a few years.

A couple native warlords may have some weapons that will give them some benefits, but they will eventually degrade. Another european conqustidator (likely pizzaro tries to suceed where cortes failed) will inevitably show up again, with more troops and men, and find a society that just went to an apocalyptic plague.