The leaders wanted to be rid of Jesus, but the masses turned on Him also. Remember, they had a chance to grant him the Passover pardon, and the crowd picked the Barrabas instead.
I doubt you could say “the masses” — more specifically the crowd gathered in front of Pilate. This could have been a specially bought crowd, yes “bought” by Cleophas etc.
Not so sure this works out that way.
The crowd at the governor's palace was not necessarily a representative sample of the Jewish populace. It would have been extraordinarily foolish of the Jewish leaders to not have as many of their henchmen as possible in this crowd. The remainder would have probably been largely city rif-raf. As in today's city mobs, most "solid citizens" are busy elsewhere with their lives.
And even those who were not predisposed against Jesus might have been easily swept up in the peer pressure of a mob setting rather than making a concious decision to reject Him.