I think searching for "The root cause" is moot. Imagine a car that has a construction flaw in the driver side door. A strut in the door breaks easily when rammed and forms a spike towards the driver. If you are driving this car, you are more likely to be injured in a crash than in a car that does not have this flaw, right? Yet, the "root cause" of your injury would not be the construction flaw, but the force applied to the door by the other vehicle. Now imagine fans of the car after this had lead to a tragic accident, telling everyone that it wasn't the flaw in the car, the driver of the other car should have been more careful. They are right, technically. Yet, denying the higher likelyhood of inflicting such an injury due to the specific characteristics of the car would be missing the point somewhat either, woudn't it? I think it's the same here.

We have to acknowledge that weed will be more likely to cause an addiction (not only of the habit variety) more easily than other things. Going off on the "but weed itself does not form addictions" bandwagon only belittles those who have an addiction from it from the perspective of the addicted themselves.

By that logic, nicotine is hardly addictive, neither is cocaine nor caffeine. When talking about addiction, we sometimes tend to only count the physical addiction formed by things like Heroin as "caused by the drug" and to blame psychological addictions on the user's psyche. That's what the war on drugs taught especially Americans. Yet, psychological addiction is the more prevalent type of addiction and it is way more likely to form - regardless of one's tendency to form addictions in the first place - in substances that get you high in some way.