Well, if you tipped your head in my cardinal direction during the night I published the final chapter you would have heard the "thud thump thump" of me head-desking as realization set in...
On a more serious note, it was a mix-match of "hmm I have a lot of unused notes here" and leaving the fic I exited with more questions than answers irritated the heck out of me and left me realizing that if I wanted to wrap it up I really needed to wrap it up.
Basically, I started the tale as a tale of two men, middle-aged and both reaching midlife crisis stage respectively, trying to get over their trauma and reconnect after some very different life choices that left them morally opposed on almost every subject that mattered but them still making their friendship (the only stable point in either of their lives) work.
The story ended with an international threat level 'mon getting triggered, put down/contained, and the focus swinging away from a slightly hostile and diverse cast to a very flawed world stage that had let things get to such a disaster point. Basically it went from two old men prepping for retirement to them having to band together, take stalk of their resources (two young trainers, a small hometown community, and a scratching of a syndicate), and realize it was them against the powers that be. Powers that sat on their hands while the apocalypse was kicking up in their own backyard, and it's looking more and more that their governments were either inept, corrupt, or selling out to a more powerful Region who was gunning to kick up international war.