There's an excellent and fascinating book that describes, among many other things, how the satellites were saved from being "de-orbited" (crashed) about 20 years ago. It's called Eccentric Orbits.
Yeah, I was at Motorola when they were supposed to be deorbited. I knew a guy that worked in the lab when they went through the lab to start to destroy all the equipment as part of the liquidation process. He saved one of the iconic brick handsets for me. No sim card. Just Accelerated Life Test Unit 4. It's been a proud possession of mine for years.
https://www.amazon.com/Eccentric-Orbits-Iridium-John-Bloom/d...