I do agree, but this arrangement was probably done long before Astral Chain release.

What kind of logic is this? Astral Chain sold more than 1 million in the first 6 months, making the second fastest selling Platinum game, just behind Nier Automata(Correct me if I'm wrong). It's probably around 1,5 million at this point in time.

And Platinum is probably the one to do a sequel. Just because they sold their share, it dosen't impede them from working on a sequel, much like Bayonetta 2 and 3. And even if they weren"t behind the sequel, Nintendo has more than enough talent to work it themselves.

Plus, why would Nintendo buy full ownership, just to stash the IP away?

So Splatoon, Arms, Pikmin, Ring Fit Adventure, Fitness Boxing, Animal Crossing, Xenoblade, 1-2 Switch,  Fire Emblem, Donkey Kong Tropical Freeze, Clubhouse Games, Marvel Ultimate Alliance 3, and more exclusives all sold poorly? These franchises are all dead too cause they sold around or more than Astral Chain?

I understand your point but...  why did you bring Animal Crossing, RFA and Splatoon? They sold many million copies even in their debut games 

I dont think you get my point. Im talking about the cost of a game. You cant just suddenly make a 2D Astral Chain for cheap and have fans be happy. It would take a lot of money, manpower and time to make a sequel to it. Most of the games you mentioned are not very expensive to make. Well except for Marvel Ultimate Alliance 3, which yes, I also think is dead. At least for Nintendo paying for the exclusivity. If you want to keep the dream of Astral Chain 2 alive, then thats cool. I really liked the first game and would like a sequel as well, but Im not holding my breath. But as someone said in here, it is possible that PG will ask Nintendo to do a sequel. In that case it might happen. They just dont seem very keen on working on exclusives at the moment.

Edit: I guess Im being a bit too negative and overdramatic. Its just I dont feel like this franchise is a good fit for Nintendo. Like Eternal Darkness. Now that game didnt sell that well when it launched, but it has obviously gotten a big cult following. Nintendo could easily do something with that franchise, but they just dont have a team with that kind of experience. Same with Astral Chain. Its like they need PG to make it. Would be better if PG themselves got the rights to the francise I think. They would know what to do with it.

Wtf? AsCh was in the works for fours before it was even revealed it went on to sell 1m on its debut more than what the likes of Xenoblade even managed LT for its first game now lets buy it to shelve it and never look back? Even the whole it doesn't fit them argument is just as bizarre as if companies aren't supposed to diversify or change for different eras.

Many games have also moved on from the original teams look at Devil May Cry, Tomb Raider etc... If PG don't do it someone else will.

 I'm sure Nintendo only did the deal because they own 50% not because of a need, most likely Platinum moving towards self publishing instigated the move to gain W101, and along the way it ended up involving them offloading their share of Astral Chain, most likely because part owning an IP with Nintendo who also own the publishing rights seemed out of step with their move away from contract work, so selling their share gave them one less complication to deal with why they embark on what they see as their future. 

The same people who think Astral Chain was a failure probably said the same thing to Arms.

Its not a failure. Just decent by Nintendo standards.

If the sequel of AC and Arms sells close or more than the original then I can put them on the same tier as Xenoblade, Yoshi and Kirby games (Maybe DK and FE are also on the same tier) Which are all successful franchises.