Well placing the percentage of blame is something of a moot point but I wonder if you'd feel the same way if this were 2 cars instead? Or a truck instead of a bike with the car driver dying instead? If those change your answer then you might want to reconsider your thinking
One of the lessons I learned while I was riding was to act as if half the people wouldn't see me and that the the half didn't care
That one concept alone saved my hide numerous times each day. Bikes are hard to see and even moreso when most people aren't looking for them which many drivers aren't
Regardless that, it is
still the responsibility of all drivers to look for and see any and all dangers, and to
never place their vehicle where they cannot know positively that this will be a safe thing to do. That requires looking, seeing, and thinking before moving of which the car driver obviously failed at least the first 2 of those. Would such a car driver as this look for and see a small child wandering into their path if they can't see something much larger like a motorcycle? Hmmm- makes you wonder, doesn't it. Especially if it was your child
The biker was acting somewhat suicidally with the excess speed which most certainly did amplify the consequences of the crash, but I'm fairly certain it would have occurred had he been going half that fast simply because the car driver failed to look and see before moving. Remember-
several other drivers there clearly saw the bike approaching so why didn't this one?
Hard to see, maybe but not impossible
The sad fact is that the vast majority of vehicle operators are not paying adequate attention to their driving and the situation around them. Driving as safely as is possible almost always takes nearly 100% of your attention (and more would be welcome if it were possible). Rare is the crash where the true basic cause was not at least one person paying inadequate attention, and because that is preventable I now call them "crashes", not "accidents", because
they aren't accidental at all They are crashes, usually unintended ones, and usually caused by at least one persons
intentional but errant actions.
Operating any motor vehicle safely isn't easy to do yet we must all do that to the best of our abilities or we get sad results like this which nobody wants.
Phil