There isn't much of a question to answer but I wanted to document the evidence that the correct answer to this question is in fact the Safehold series.
While you've done nothing wrong, with changing the dupe target, and it was probably a safe bet to do so, there wasn't really a need to.
We can break the timeline of events down into two specific time periods:
- End of March 2014 and initial acceptance,
- Beginning of January 2016 and change of acceptance.
End of March 2014
Two answers were posted around the same time, the first by JohnP suggesting Helm by Stephen Gould. The second by Oldcat proposing David Weber's Safehold series. With these two synopsis at hand, the OP had felt that Gould's Helm was the closer of the two, stating:
This is the one! This sounds exactly right! Wow! So excited to read this now!
ArtSabintsev - March 27th 2014
From Art's wording, we can guess that it was a closer match as opposed to the objectively right answer.
He'd also granted JohnP the accept on the same day (as time goes on the page number will change, the accept is noted under the rep for the post in quetion on the 27th of March 2014)/
Beginning of January 2016
The question stayed in this state for close on 2 years, until another user, O.M.Y, answered on the 7th of January 2016. This user was adamant about the book the OP was looking for being the Safehold series and provided a separate synopsis from the one provided by Oldcat, going on to explain his thoughts on why it couldn't be Helm (too old for the New Releases section) as well as providing the name of the protagonist and the book titles.
With the additional information, the OP returned and exclaimed his joy at O.M.Y. confirming it was in fact the Safehold series, stating:
YES! This is it!!!!!
ArtSabintsev - January 7th 2016
... Reading your description jogged/jiggled my memory - this was exactly what I was looking for. Thank you so much!
ArtSabintsev - January 7th 2016
After O.M.Y's answer, ArtSabintsev granted Oldcat the accept and in doing so knowingly unaccepted JohnP's answer (as above, documented on January 7th 2016).
From the passage of events it seems clear ArtSabintsev is certain the series is the Safehold series, and the similarities in the Helm book was just a slip up on OPs part.