Similar problems in Turkey at some points during the 20th century. Army views itself as the ensurer of the secular state and relinquishes control when it appears a legitimate secular state and internal support systems are in place. Trouble is, army often steps back in.
I'm not surprised something like this happened. Was more surprised over the speed with which it happened, both in terms of how soon during Morsi's term the intervention took place and how quickly the army established control. Egypt has a very interesting history. It's where a lot of the more extreme (read conservative) interpretations of how Islam should interface with government and at the same time, it's been a crossroads between East and West for centuries.
For the West, stable regimes have almost become an obsession and I'm sure that's in play here.