For some reason I start to think their metrics logic is too stupid or outdated, or they need another standard of success or monetization (like kickstarter, patreon, or anything thats is more reachable to the fans to get an opinion of investment)
I don't work in the industry so I can only speculate, but many of these publishers release both manga and light novel. I think the process is simply something to maximize short-term profit: find a popular work on syosetu; publish a light novel out of it; wait a bit to see how fares and make a comic adaptation with an initial short amount of chapters to further advertise the novel even to people who might now follow novel news on the regular. There's probably some agreement that if the comic goes well the adaptation is extended, which would explain why these works end abruptly: the mangaka works with the intent of keep going, an organic end means failure to deliver.
To add to all that, almost all of these adaptations are published on digital platforms, effectively at zero cost. They don't have to print paper or take space on a weekly or monthly magazine; put the finished chapter on a server somewhere and rack in the money from the in-site currency or whatever. Digital releases are also the reason why many works have split chapters, exactly to make readers spend as much in-site currency as possible.
The metric of economic success then is simply whether the work manages to make money according to the short-term strategy.
That's my guess, anyway.