TIL in 2013 a California power substation was attacked by gunmen. The attack appeared to be "a professional job." There are no leads and no arrests have been made
This one I'm not sure, but the NC one was done by a far-right conspiracy believer. It's also been done by some of the far-right militias that have popped up in the last decade.
They do it because they think it'll destabilize the country and start a civil war. One they want to win so they can inflict their ideology on everyone nationwide, whether it's wanted or not.