The BBCs radio network is an important piece of national infrastructure, it's supposed to be resilient because it would be used in a national emergency. That's why a massive failure caused IIRC because there was a single point of failure is significant. Plus of course having almost the entire distribution of 5 radio networks depreciated isn't great for the listener
Forcing the whole thing into a DR scenario amd part of that not working is a pretty big event.
I do remember that afternoon, we were on a trip to the coast listening to Radio 2.There were glitches that I put down to the car radio's RDS getting confused by lift conditions (it was a hot sunny day, (which of course was the trigger event))
It wasn't until we parked up at our destination, and I had a proper fiddle with the radio I noticed the RDS IDs were indicating RBS mode.
The effects were probably unnoticable by most in London and the SE, it was further north (and everyone north of the Midlands losing Radio 1 because of a separate problem at Sutton Coldfield) that the punters were affected.
The report makes interesting reading, it reminds me of many air accident reports where there are multiple events, none of which on their own being catastrophic, but when combined.....