So it's safe to say the 30% that left bitcoin did it's damage by clogging up the network
What damage was there? Bitcoin worked and is working as it is supposed to.
It seems to me that the only damage done was to the reputation of those who moved their hash rate to an alt coin. But that too is fine as they are free to do that.
The BTC network slowed extremely down during the weekend, causing the mempool to fill up like rarely seen before. So no "damage", but still a major disruption of service.
I think this is still not over. They're testing the limits for sure. but it seems like someone will profit greatly out of this coordinated attack.
Yeah, I also have a feeling that this is not the last we've heard from BCH. I wouldn't go as far as calling it an attack though. It's simply what happens when multiple coins share the same PoW hash and one gets pumped. Arguably it shows a merit of BTC relying on ASICs instead of GPUs, because otherwise BTC would be forced to battle with other alts for computing resources as well.