I think the point of OP, and of the other magazine article linked in the comments, is that he hasn't 'grossly underestimated' it in the least bit: yes, you can pay peanuts for Iridium and run an already built Iridium network on those use-cases like the military and occasional people going to war zones and NGOs and hikers, and make the business work that way. But you cannot build one costing billions of dollars based on those use-cases, which is why Iridium went bankrupt in the first place - their business plan was based on covering way more than lost hikers and Afghanistan, it was based on the delusional ideas that businessmen in Paris would pay for it. This was delusional, so Iridium went bankrupt, defaulted on its debts, cost its original investors fortunes, and had to be rescued out of bankruptcy for $25m and refocused on the use-cases which actually did work.