Why is my MacBook shorting out?

I got a 2015 retina macbook and the only thing wrong with it is that the computer was opened wrong and the cables tore. I replaced the cables I thought looked damaged and now everything turns on except the display. So I started messing around with the cabels trying to find where the problem was and I found that when I unplug the cable going from the track pad to the keyboard the screen turns on and even the mouse works. When I plug the keyboard back in the screen, track pad and the keyboard turn off. But external display still works. Wondering if the whole keyboard is garbage or just the cable? Or is it the logic board?