Naval Nuclear Laboratory Technical Writer interview questions

I applied in June and was asked to come in for an interview in early October, following a 30 minute phone interview about a week prior. The interview took half a day and was very extensive. The questions were mostly about how you'd handle certain situations and a lot of very candid comments about the culture. All of the interviewees spoke to me as if it were a great fit and I'd most likely be hired. When you wrap up with HR, they say that on average a decision is made within 3-4 weeks. That's understandable since interviews take half a day of everyone's time. However, five full weeks past and after following up several times I got an answer that they were still interviewing. Finally, exactly two months to the day after interviewing I received an email that I would not be offered the job. It seems like a good place to work with a lot of benefits and a great schedule but I imagine the extremely slow pace might be hard for some people.