It's only my guess, so could be way off the mark. I think we are all sensitised to the way many car drivers and passengers just open doors without care, unfortunately. You often need to open the door a small way to see properly - certainly I do in my car as there is a blind spot in the rear quarter that neither the interior or door mirror cover. If, as reported, this driver did that, yet the cyclist, quite reasonably assumed that the door was going to continue to open in front of him, then I think it's conceivable that he might have swerved and perhaps braked, so, perhaps, causing the loss of control that led to him being killed.
There's a strong argument that says that this accident was caused by the known careless behaviour of many drivers and car passengers, who have conditioned cyclists to anticipate being doored when passing parked cars. Sometimes that anticipation might be the very thing that saves your life, but I have a feeling that in this case it may well have possibly had the opposite effect.
Sadly, many accidents are just that, accidents, with neither party being really at fault, as implied by the judge's comments in this case. I don't suppose this will appease the avid anti-car brigade who aren't really interested in the particular circumstances of this accident. My guess is they will go on howling for motorists to be strung up even if they aren't demonstrably at fault.