from the news report I could believe it's both a state actor, and primarily designed for fraud, but I do also believe there's an attack risk in simultaneous cell flooding. How much that magnifies into a real risk I don't know. Sports venues routinely call in mobile microcell vans in S.E.Asia (I've seen them in Taipei) to backfill when 10,000+ people want to ring mum from one location. So there's some capacity-risk issue with simultaneous use.
I also think that basic heat-maps of L2 signal strength and seen IMSI would have been a very strong clue something was up. If you put the city overlay into a GIS and heatmap the cell towers and binding states, you'd be going "hmm for a 10 household building, with 1000 simultaneous cell connects.. WCGW"
What if e.g. flooding the 5G/4G state forced people on roaming profiles to use weaker protections in a 2G space?