Fried electrical system?

Nope, the battery terminals are marked correctly by the factory. It’s been like this for the past few years and nothing like this happened. I did the hookup because the car was imobilized in a parking garage.
And BTW, you can’t hook it up backwords in the car because the leads are too short , even if place the battery 180 degreees from normal position.
Anyway, I have the battery with the revered polarity as prroof of their incompetence.