Why did some of the native population join Cortés in capturing their own capital?

Answer:Native American Gave Cortes Slave's A Gift Is Because They Did Not Want To Get Hurt And just want to Be Cool With Them For Know One Of A Native Americans Wouldn't Get Hurt And Also They Was Sick And Tired Of There People Getting Hurt Ans They Didn't want No More To Get Hurt There Is Some More Stuff

The correct answer to this open question is the following.

Some of the native population joined Cortés in capturing their own capital because some Native Mesoamerican Indian tribes had to pay tribute to the Aztec Emperor. The Aztecas were great warriors that conquered many territories. Those conquered territories had to pay tribute to the Aztecs. We are talking about Native tribes such as the Tlaxcalteans and the Cholullans, that saw in COrtés, and opportunity to defeat the Aztecs and free themselves from the oppression of the Aztec Empire.