So, I watched Tatoruzu recent video, however I want to chime in a little towards the end of his video.
The word he was looking forward is 'decompression', something that has plague the overall comic industry since either 1999 or the early 00s. That is why not only volume 4, but IDW'S run moves so fucking slow. Granted, volume 4 seemed more like it ended when Peter was getting tired or burnt on the story he was telling; basically meaning that he ignored what others were doing by telling a story dragged out over a specific amount of issues and then compiling it into a trade paperback. This leads us to...
IDW'S RUN (or just the first 12/13 issues). These comics are essentially the personification of what I was talking about;
where nothing happens substantially in a couple of issues before it gets to either its fifth or sixth issue of their trades. I don't know the exact sales of either of these two, but I'm pretty confident that the trades of IDW sold more than its initial issues.
Hell, look at The Last Ronin, that series also had drag out its feet before the final issue. But, that's another topic for another time.
In terms of the comic medium as a whole, I don't want to say decompression is necessarily bad. With that being said, the past two decades have either done it poorly or sloppy. There is no other alternative. People have no grasp of how to format comic books anymore. (Sighs)
Anyways, I hope you understand a little more why that happens pretty often now. I may do a more in depth post on decompression as a whole, but not today, I won't.