I wonder what Iridium could have done better, if they used more agile methods and followed the market. Sure, they could have discovered it wouldn't work half way though, given the remaining money back to investors and closed down. But what company does that?

I cannot really see a good "minimum viable product" to test the market for Iridium either. Nobody would buy a phone that only works for an hour each day, when the first satellite in orbit is overhead.