Then he stood up to welcome Cortés; he came forward, bowed his head low and addressed him in these words: “Our lord, you are weary. The journey has tired you, but now you have arrived on the earth. You have come to your city, Mexico. You have come here to sit on your throne, to sit under its canopy.
After Montezuma told Cortes this speech and for him to understand the intentions of Montezuma why would he start the attack on the unarmed musicians. Montezuma gave up his kingdom and was allowed to be prisoner all because they believed the sun said so, so why would Cortes still attack after they gave him a free city to control.