Yup, that’s almost certainly it, I’d suggest. Internal politics of some kind. Supposedly teams within Blizzard have pretty decent decision-making power, and if whoever was in charge of D4 said “Nah, think not” to Blizzcon, quite possibly at a very late stage in proceedings, well, they were going out there as one of the first panels on the main stage with dodgy-looking non-Blizzard-developed mobile game. Goddamn. I suspect some people are no longer friends at Blizzard.
One interesting thing here has been the behaviour of the press.
They’ve been consistently more “JEEZ GUYS Y U SO UPSET?!” than fans, and Kotaku semi-intentionally revealed why the press “don’t get it”. It’s because, as Kotaku mentioned (the only press outlet who has said this), Blizzard have off-the-record confirmed D4 is in development. Whereas when Immortal’s stuff came out, a lot of fans did, and some still do, believe that D4 may have been abandoned. Which puts a very different spin on things.
I do think it’s a bit shitty that Kotaku were the only press people with balls to come out and say “Diablo 4 IS in development, Blizzard sources have confirmed” (Schrier has a rep for not getting this kind of thing wrong, too, much as it has made Bethesda hate him). I’m not talking about RPS. I can’t imagine Blizzard do off-the-record confirms for them, necessarily, but it’s clear from some other articles out there that journos are MUCH more confident D4 is on the way that most fans have been. So when they’re critical of fans for being overzealous (and they weren’t actually that bad here, whiny and pissy but not really extreme), whilst have this secret information, well I think think that’s a bit crap, because every single critical article I’ve seen has been based on “Well OBVIOUSLY D4 is coming out!” and I don’t think it is obvious or certain, well wasn’t until Schrier let the cat out of the bag, as he often does. So two thumbs up for Jason Schrier, I guess!
It’s still an intensely bad decision. They would genuinely have been better off announcing this say, two weeks after Blizzcon, and just having the Switch version (by all accounts excellent) at Blizzcon. And people must have known that. Some utter wankers somewhere signed off on hanging people like Cheng out to dry here.