Montezuma sent gifts to Cortes on his arrival, he sent him god clothing and apple filled with human blood.
They decided to join the team of Cortes to defeat the Aztec.
Fine we will join your team!
One of Montezuma messagers came with the gifts, Cortes put on the god clothing to show that he was more powerful than Montezuma but refused to eat the apples because the thought he might get positioned
Cortes needed a bigger team to defeat the Aztec, so he went to the tlaxclans and the cholubla and treated to kill there leader if they didn't join him