While we don't know exactly what caused the winning streak, it seems clear that a key part of the winning streak was related to Zava being on the team. We know that Jamie is overshadowed by Zava's stardom which tells us that Zava is a star, and we see that Zava was mentioned in relation to the winning streak. Therefore, we can guess that Zava joining the team helped the team to go on a five-game winning streak.