Burnt out Distributor Rotor

[lugbutz]

Hi
I was working on the car, replacing ignition cables and checked out the distributor when I noticed a couple of things.

1. The Distributor cap had a huge chunk out one side where the number 1 ignition cable should go. It looks like this
https://drive.google.com/open?id=1zYqi3 ... V1zJSsaTda

Inside the Distributor cap looks like this

https://drive.google.com/open?id=1DrFq2 ... BA7Y_YfxRN

2. The Rotor its self looks like this... To me it seems that there was a short or something
https://drive.google.com/open?id=1dv8Z- ... ivddldSiWR


My question is why did this happen and can I prevent it in the future?