The authorities quoted in the article said whoever did it had a good understanding of the power grid and what they were doing. Maybe it's common enough knowledge, I don't know but it gave me the impression that it wasn't trivially easy to do, making copycats, especially by just the kind of dumbass who would copycat this, less likely
I addressed this in the rest of the paragraph you commented on. I would prefer not to go into detail on the mechanics or the specificity or sources of the instructional materials.
Extremist corners of the Internet have been discussing how to do this for several years down to even suggesting certain substations for maximum impact (thanks in part to gov reports on the subject). It's surprisingly trivial once you learn about it.
