Oh wow. Looks like someone peeled the shrinkwrap off that battery, and ran the bike without it, exposing the cells to potential short circuits, and the BMS control board to the world. Very dangerous.

One could replace the throttle wiring with properly soldered/shrink wrapped cable, but I do see a couple of hanging JST connectors there,

There is the one trick of plugging in the charger and see if the bike powers up and spins the motor with wheels off ground, That will tell if the controller and its wires are working, maybe.