IIRC the Go / Now switch was due to Go being the app if you already paid for cable and wanted to watch HBO by logging into your cable provider account. Now was the pure streaming option those without cable could purchase. Took a bit to consolidate I think.
That was the given reason, and I'm sure they knew it was ridiculous and fixed it as soon as they could get all their ducks in a row, but it sure was comically bad from the outside perspective of ordinary users. Even if there had to be 2 apps for some contractual reasons I think most people would have been more tolerant if they had identical functionality and appearance after login, and were just titled "HBO Go for Cable" and "HBO Go Streaming."
I could imagine HBO Go starting off as literally their cable package "on the go" with no intent to ever charge for streaming, being able to login at others houses or on vacation to enjoy your paid package etc. Then another team / project starting up the streaming option and went with Now and I wouldn't be surprised if it was indeed all contractual reasons.
