Aw, I didn't realize till now it was on hiatus. Obviously a bit sad for us but at the same, if that's how the author felt, much better to put it on a pause then force it.
Only speculating, I know very little about the behind the scenes, but I wonder if it's a combination of what various people commented on above, about the pacing, about how it actually seemed like progress was finally being made, and I wonder if the pressure of landing what has actually become a very well-done slow burn was getting to the author. You only get that chance once, maybe it just was tough getting it just right.