Also - Steem was mostly pretty flat during the time of the SBD boom in 2017. It's my view that eventually excess SBD value was channeled into Steem by a slow mechanism, and that's what caused Steem to have a boom significantly after the rest of the crypto space.
A full causal analysis is very difficult, but we are in a unique position where Steem vs Hive is nearly a like for like, A/B test. Perhaps with a few months more time we will have the kind of data that we can say with confidence what kind of causal link there is if any.
I'm looking forward to a potential analysis in the coming months. I think i said similar a few weeks ago, but the best data might come to light at the end of the bull market - SBD swinging high then low, and hopefully HBD not going too wild in either direction.