You can blame BAES if you wish, blame the government, blame life - blame everything.
A company THAT large does move like treacle, and in the course of these large projects the world moves on, things change.
Governments change, policy changes and the Armed Forces have to change in accordance with the latest policy shift (which may or may not be justified, but they are the Lords and Masters).
So the goal posts shift. It's not really anybody's fault, it's just life.
40 years ago, saying jobs-for-life would disappear would have been treated with derision. Sadly, it's the world we now live in.
But, if it makes you feel better, blame BAE. If not them, WHO are YOU going to choose? At least the jobs are generally British ones.