For all you know you may have been distracted by the indicating vehicles, you might have noticed a bit of ice on the road, you might have just remembered that you'd left the gas on, you might have noticed a spectacular offer in one of the shop windows, you might have noticed the dancing monkey etc.
(Yes its another caricature...)
They're not "caricatures" as you put it, Mags. Gaz could have just checked his shoulder, looked down for potholes, spotted pedestrian movement to his left, wiped snow from his eyes, had issues with glare etc etc. I'm not saying any of these possibilites played a part, but we should not forget that our brains are tying to make sense of competing stimuli
and prioritise accordingly. When we know what's happened we can easily stitch things together and forget about other factors that might have played a part at the time, but cannot be so easily dismissed when you're
actually cycling as opposed to watching 720 vids at home.
Watching a vid over and over again allows you to piece cues and clues together - in real time, in a dynamic traffic situation you will not always get it right; as a
cyclist human being you
must expect a degree of cognitive failure or overload, no matter how defensively you think you ride. If anyone thinks otherwise, they're deluding themselves.