Why is the Bishop so big


See in Russian, it's слон, which translates to elephant.
I'm guessing as the game flowed away from India, some changes were made per culture.
To start with, the bishop may have been a camel, the rook an elephant, the pawn a soldier. Maybe in Russia they felt the elephant could replace the camel and introduced a tower in place of the position formerly occupied by the elephant. I'm no expert on this.

Yes, actually we do call the bishop camel, and the Rook elephant here. I have no idea about it formerly being an elephant tho.