The costs of building and launching small satellites has dropped significantly since the 90s. People are also traveling more and demanding more connectivity, so it seems that Iridium may have just been a bit to early to the game.
Iridium service was also unbelievably expensive and not all that useful. (For that matter, still is.) If you had a choice between Iridium and a cell phone, the cell phone won every time. Iridium was a product for those with no other choice. If they had come in earlier, they might have had enough people with no other choice to make it. Later, and they might have been able to offer something that could actually compete with terrestrial services. As it was, their timing ended up being really bad.
Very useful if it's the only thing that will work.