Conversation so far:
When did the Spanish colonization of Mexico begin?
The Spanish conquest of Mexico is generally understood to be the Spanish conquest of the Aztec Empire of 1519–21.
What happened during the Spanish colonization of Mexico?
The Spanish conquest of the Aztec empire.
What was so spectacular about the Spanish conquest of the Aztecs in 1519?
The fall of the Aztec Empire was the key event in the formation of the Spanish Empire overseas, with New Spain, which later became Mexico.

Question: What else happened during this time?
Self-contained rewrite: What else happened during Spain's initial conquests in Mexico besides the formation of the Aztec empire?