Why did leaders in Jerusalem arrest Jesues?

They arrested him because they saw him as a threat to them in the side of religion and because the people were calling for him to be arrested. And as per the tradition of the feast that was happening at the time, they asked Pontious pilot to release the murderer barrabus instead of Jesus who had don no wrongs other than tell the religious leaders what they were doing wrong in the eyes of the father.

Because the chief priest and Pharisees saw him as a threat to their self proclaimed authority