How was the turnaround accomplished? By firing everyone in charge, and replacing them with people that could actually make reasonable decisions. Some lower level people were also let go; we had some people without the chops to do the job. But that was not the main problem. The problem was consistent management focused entirely on 'process' without regard to what we were trying to accomplish. In the form of "MIL-STD-1234 says we have to produce documentation in the form of X. Therefore, produce X". Documentation does not result in a great product. Documentation can only, wait for it, document what was done. That was just one sliver of it, but entirely representative. Methodology X, process Y, 5 levels of sign offs all focused on what color ink you used or if your document's headers use the right capitalization. Just shuffling requirements along an endless document chain, without actually trying to figure out how to meet those requirements.
A really smart systems engineer who had the bosses ear was able to say 'they will never make it', he eventually listened, she was put in charge, our best engineer was finally put in charge of the SW, and from there we recovered.
In the interim we hired a bunch of outside consultants to come in. I don't see that they did anything of value. Lot's of interviewing, lots of 'do x, y, z'; meanwhile the people that had successfully produced this sort of project before were still being ignored.
That is one story. The problem was mid-level management, and only once they were all fired (actually, there were several rounds of getting rid of person A, and replacing them with an exact clone, and of course that person had identical results) did we recover. This probably doesn't apply to any place where the problem is not middle management (say, a team full of cowboys, or a PM that sends you off on wild goose chases, or whatever).