I am not sure but i think.
Rail bridges have 2 tracks max in general.
And many rail tracks going through that area.
To make easy changeover of tracks and avoid collision tracks may have curved before routing it to single track on bridge.
This is my own thought, i never worked on railway nor study in depth.
One day you will become a great engineer because you have great fuel in you to get develope further called as curiosity.
Only curious people do ask question, rest are just a follower of them in this real world.