I also believe that the ending was rushed as if the series was soft-cancelled. There were a lot of plot points in previous chapters that were obviously meant to be developed later, like allusions toward Hanazawa's drinking problem over the death of her sister. I expected a resolution more like Todd and Alice in the original game. Instead, it was closed by punching out the problem. Very uncharacteristic of the story development until now.
My personal impression is that the series was not that popular. Just based on my interactions in other communities, even this translated version had trouble among English-speaking fans. It would have flare-ups of activity, and then very promptly be forgotten. Quantic Dream itself may have been a factor as well, as they never properly developed the series for the Western audience. The manga even reads left-to-right, which to me is a sign that they had intended to officially translate and release it at some point. Not sure what happened. It's a shame because the writing and art were good. It had potential to give fans one more nostalgic run with the Detroit universe.