I'm fairly certain that the Hive witnesses had already been planning to fork for a long time, and they were just waiting for an excuse, so they went all-in on FUD and misinformation when they launched their attack.

I suspect they had been planning on eliminating or redistributing Steemit's stake, which is why Ned wanted to sell, but they probably wanted to keep control of the chain rather than building a new one. They probably expected Justin's response to be something that forked the chain, and then they could claim that theirs was the "real" Steem chain and Justin was the one splitting off a new chain.