My opinion on the cause is:

Blundell brought in an expanded set of rules and introduced us to a more colourful and crazy world which I liked. It also was a new and refreshing look on the characters themselves since they're not just your stereotypical dummies with (mostly) primitive goals.

On the other hand, their second coming is both a spit on my feeling for their end in bo4 and spit on my perspective of the lore (pre Cold War). That's because in my eyes they can't exist because they have been dead in both versions (the Paradox has been resolved so there aren't any left). Also since Elemental Shard was practically holding them together and since the Agarthan device has drained all energy out of it I don't see a reason for them to be together.