“In total, law enforcement discovered 300 SIM servers – over 100,000 SIM cards – enabling encrypted, anonymous communication and capable of sending 30 million text messages per minute. Officials say the servers were so powerful they could have disabled cell phone towers and launched distributed denial of services attacks with the ability to block emergency communications like EMS and police dispatch.”
First of all, I imagine the budget for state-sponsored espionage and interference is quite high. They may have also not been tied to your typical postpaid plan through a major carrier. You can get prepaid lines and different types of service, such as for IoT devices. These may be a couple bucks per month and are meant to send messages and generally small amounts of data for decea such as SmartThings trackers.
Edit to add: but yeah, 100k SIM cards does seem like a lot. They could probably create havoc on the local cell towers.