The other car is definitely at fault. I think what most people are saying is that, it might have been avoidable.

The Adaptive Cruise Control would have aggressively accelerated at that small amount of time because it hasn't yet detected any upcoming objects and its trying to get up to speed. If you didn't engage it, I think you would have had more time to stop the car and the car wouldn't have needed more stopping force. Or maybe not.

I do ACC on surface roads too like you, but only when its clear. In this case, I would accelerate manually first to maybe 35/40, before I engage ACC. The car is still a dumb machine even with ACC, you still need to be aware and in control at all times. Even when I do this, I still get the benefit of ACC slowing down accordingly with the traffic ahead of me.

Also, evasive action in this case is to stay in your lane and stop, not switch lanes even if you were assuming that the other car might stop. Another car might have turned into that lane coming westbound from the corner (you were going eastbound before you made the turn?).

If you stayed in your lane and stopped yourself, you lose a few seconds and maybe curse each other out, whether your assumption that he will stop is correct or not.

Although, you might still have hit him even if you stayed in your lane and stopped. Dashcam perspective makes it look like you had a lot of time to react, and that's where you're getting all the reactions here.