No. I mean shingeki rising from unknown manga to popular so quick. I'm not count from its first chapter, I count it from when it still unknown(it's different) look at
July 2010 Shingeki sales was not impressive at all. that mean its start gain popularity after that. and in Dec Shingeki went from 30k to 180k tank sale. just 5 months(but I believe it actually less than that) sale was increasing around 6 times, I would say it
quick
How is over a year quick? What does that have to do with moving to another magazine, anyway?
About Koe no Katachi I agree with @Kaizou 10. editor want it public and it's a reason. but don't change the fact that Koe no Katachi original was in Bessatsu and become famous just because of WSM has larger audience.
Japanese readers don't care very much about magazine. That's not how they find manga. Japan also has the internet, TV, libraries, radio, conventions, anime adaptions, drama adaptions, and critics, all of which are more effective means of promoting manga. International fandom has created a mythology about magazines that does not exist in Japan. Kodansha's two best selling manga (by volume) are both serialized in low circulation magazines. Shingeki in Betsumag and St. Young Men in Morning Two. Kodansha has historically had a great deal of success developing bestsellers of varying degree in medium and low circulation magazines. It would be almost wholly irrational to think that after decades of success promoting manga in lower circulation magazines, that they would suddenly change course for one, and only one, specific one shot.
Kamisama part 1 probably
as popular as Shingeki but no single volume manage in top 50 oricon chart. why? most possibly is Bessatsu don't have big audience enough to promote this series. you may think editor just hype it. but I don't think so. as for your last question, I think they're no worthy series to transferred for.
Wanna buy a bridge? I have one in Brooklyn. It's for sale, if you want it.
I believe it because Bessatsu's questionnaire made editor believe that(I think because of most Shingeki fan didn't buy bessatsu back then) but still, having good result in questionnaire don't mean it sell well. just mean it had potential. but yeah Kamisama part 2 is more popular than part 1 was and even helped part 1 sales. I guess editor chosen a right choice.
Most Shingeki fans still don't buy Betsumag. The most recent published circulation was 60,000 copies per month. That is not how many copies sold, but how many copies printed.
Shomag editors don't have the right to poach manga from other magazines. That would be a disaster, undermining Kodansha's other publications. Mangaka are under contract, they have obligations to the magazine they are in. Shomag can't take what they want, when they want. The other magazines own the rights to their titles. We don't even know if Shomag approached the mangaka of Iutoori. When their contract expired, they could have approached Shomag about moving serialization. There is no way of knowing who approached who, or under what circumstances the move was made. It certainly seems very doubtful that popularity, or potential played any role in the move. Iutoori was not popular when it moved. Kodansha has many other shounen magazines, many of which have titles with as much, or more, potential than Iutoori. Why Iutoori instead of Kaibutsu Oujo, Pumpkin Scissors, Noragami, Yozakura Quratet, or any of the many other titles from Magazine Special, Monthly Shounen Magazine, Shounen Sirius that have shown potential? Iutoori is not the first monthly Kodansha shounen with commercial potential. Why, of the thousands of manga Kodansha publishes, did they select this one, specific, horror manga? Maybe it might not be a matter of popularity at all. What if it was just a good mutual fit. The mangaka of Iutoori wanted to switch to weekly serialization, while the editors of Shomag thought that Iutoori filled a void in style, tone, or genre. Iutoori's contract with Betsumag expired, one of the parties approached the other, and a deal was struck. Why must everything be about sales and popularity?
Sales of Iutoori still are not exactly high, lower than 100,000 before they fall off the charts.
Hope he gets better in the next year(s) though.