What can you infer about cortes’ motives in writing about “the wonders of tenochtitlan” and the aztecs? why did he choose to write about the topics he addressed in this letter? who is is intended audience, and how might that have influenced the letter? is this a primary source?

This is a primary source.  He wrote the letter to impress the Spanish king and his court, to convey that his expedition had been a good investment because the place was rich and luxurious, that there were gold and other riches to plunder, and peoples to force into submission to the crown of Spain. It is reasonable to expect that his letter stimulated the mind and imagination of contemporary Spaniards.

Explanation:

the passage of a strict fugitive slave law