Well no, Christianity didn't exist before Jesus. Christianity was invented because of the Jesus events.

I don't know who planned the Jesus events before hand. It was either the Roman Empire or the Jewish leaders.

I suspect it was the Roman Empire. They wanted to unify the nation and many other strategic things but most importantly they wanted everyone to blame the Jewish for the crucifixion of Jesus which would give the Romans more power. It seemed to of worked. Christianity grew and the Jews were hated forever.