This probably isn't the best answer or entirely accurate, but I usually think of it from the perspective of several different business standpoints:
First would be rewarding a series that has been showing promising growth and hopefully helping to expedite its growth to greater levels (such as Jujutsu Kaisen over in WSJ or Iruma-kun in WSC). In my opinion, this can have the largest sales impact if done correctly since a good adaptation can cause an even greater influx in readers on a per volume basis, in addition to reaping the financial benefits of those sweet backlog sales (as was the case for WSJ's Kimetsu and WSM's Gotoubun).
Second would be trying to revitalize a series that has either been plateauing in sales or just starting to decline (such as WSM's Runway and Senryuu Shoujo). Receiving an anime at this stage can be a real make-or-break situation for the series since if it fails to drum up new interest, it oftentimes signals to the editors that the series likely won't be more profitable to them than it currently is.
Third would be when a series has been facing a long-term decline in sales from where its peak once was and/or is nearing its conclusion and they are hoping for one final backlog push of sales (such as BSM's Araburu Kisetsu). These can be nice for fans since the anime essentially serves as a final send-off, almost like a "wow, I can't believe this is happening" moment. I'm not sure how often this strategy works, but I've seen it a few times, so it must work at least sometimes.
Lastly, I would classify this group as passion projects (Kanata no Astra from Jump+ is a good example). Adaptations from already completed works where you can't really think of a reason from a promotional standpoint as to why these series would be getting animated now, but when they do, you just happily accept it as fact without questioning the good fortune.
For WSS, they had a lot of series that used to be in the first category, but now ones where the sky once seemed like the limit (Komi-san) are starting to drift into the second category, and a large number of series are slipping from the second to the third level. There are definitely more factors that go into deciding what to animate and when, but from the sales-aspect of the decision, I would say it would probably be analyzed something like that.
I think that question was more in the line of, since there's limited amount of series that can get anime in a season, what makes a series deserve to get anime compared to others? How and based on what you can decide that?
I guess we can say the series in the first category (series that have high sales and actively growing) does deserve an anime because they can really take off and reach their potential with an anime. While there's no guarantee that will happen, they at least deserve a chance. Other than that everything else comes down to personal preferences.
- You can think a certain series, regardless of its sales, can really take off with an anime.
- You can also think a certain series deserves an anime just because its great or something.
Regardless almost all of it comes down to personal opinion, and probably for every series in a magazine, there's someone who thinks it's deserving an anime. For a magazine not named Jump or Shounen Magazine, there's bound to be some people who will be disappointed. And probably the one who decides to not give an anime to a series isn't even magazine itself.
I should admit, I think series actively growing and have high sales, deserves an anime. But if it's not meant to be, it's not meant to be. I think a magazine should at least try to get one for those series, but how we know they aren't actually doing that?
I am guessing Sunday would've like to have an anime for Komi-san in around 2018 too. I am sure they aren't allergic to making money. The fact that series in Shogakukan magazines are struggling to get an anime, is making me think they at least did something wrong at some point in time. But thinking again, it could be just other publishers like Kodansha and Shueisha are making the right things. Champion was truly lucky (or wise) with Iruma-kun anime coming at the right time, but the same thing happened with Takagi-san in Gessan. I guess saying they aren't as capable of them isn't true.
I am just pissed about that "big announcement" for Ao Ashi and I worry it won't get an anime. Since it's hard to find successful sports series nowadays, I hope the successful ones do get as much as promotion as possible. Because of that, I did get a little bit carried away.
Personally I would've loved to see anime adaptations for Birdmen, Yugami-kun, Imawa no Kuni no Alice and Be Blues!. I have nothing to say about Be Blues and Yugami-kun, other than similar series like them did get an anime before, so why not those?. Imawa no Kuni no Alice is a great death game series, I think it's a shame this series didn't get a proper adaptation (while so many sub-par ones gets one). For Birdmen, I think it would fit into anime format nicely, and it may do well in a service like Netflix maybe? All of this would be my personal opinion, of course, Most of them (probably all of them) won't even happen.
