If the Jewish leaders of the time betrayed the Prophet Muhammad and the Muslims of Medina, weren't there also enemies of Islam present in Medina from among the Meccans?
The hypocrites were in many places including Madina. The hypocrites were from different tribes and places including Makkah and Madina. Hypocrites used to join hands with enemies of Islam including Jewish enemies and Mushriks of Quraish and others.
Wassalam.