Well, there was the mandate plus the language itself was better than others at safety & programming in the large. The bigger reason, though, was that it was systematically designed to eliminate error from the syntax to memory handling to integrations. I mean, really thorough. Good description of all that in case anyone wants to cherry-pick safety features for use in a simpler language.

http://www.adacore.com/knowledge/technical-papers/safe-and-s...