That pizza could have been one of the triggers for bitcoin's rise.
For all you know, if he hadn't bought that pizza bitcoin's price trajectory might have been totally different.

Very good point. Human mind looking for simple solutions while they often are sooooooooooooo complicated overlapping themselfs.
Buying this pizza with 10 000 bitcoins is one person tragedy, causing global news posivite for bitcoin in longer term, which led to much higher price of bitcoin and more people involved.
You can't forsee anything almost, too many variables.