It is crucial to consider correlated variables in their correct context. This finding does not even imply impairment.

A low emotional intelligence driver, one with depression or low self worth, perhaps a psychological pathology like narcissism or nihilism. This is the type of person to initiate vehicular homicide. Intoxicant intake is a SUBSET of this group of variables.

The archetypical homicidal driver would of course have exceptionally high representation in cannabis use, and also likely cigarette use, and probably nitrous oxide but they don't measure that.

EDIT: what I will say is that dab culture is something beyond traditional cannabis use, and I could absolutely theorize that dab use in a vehicle is the new drunk driving.