It's likely not a single fault, but a fault and a subsequently failed protection mechanism. Elements of a grid usually work together, tied through frequency syn

It's likely not a single fault, but a fault and a subsequently failed protection mechanism. Elements of a grid usually work together, tied through frequency synchronisation with protection breakers to separate them if a part gets overloaded or fails. If a required generator or transmissions like did go down, and it and its users remained connected to the national grid, that load can very easily pull the rest down. Many modern countries have experienced rolling black- and brown-outs in the past ~25 years. It's not an easy thing to sidestep without a lot of spare capacity and that takes money that nobody has the appetite to spend.