Vishnu took birth as a mortal man - Ram only to kill Ravan. Ravan had asked for a boon from Lord Brahma that no God nor any demon can kill him. He thought less of men and that he can easily manuver men as they don't have demonic strength. Besides it is said that Saraswati herself sat on Manthara's tongue to convince Kaikaiye to affect the turn of events later on ...
So miscommunication or not, it was destined to happen.