I don’t believe the article anywhere tried to claim that buying a BMW turned you from a safe driver into an arsehole did it ? Therefore your causation comment isn’t really apropos.

It’s a clear case of effective marketing selecting a sub demographic: drivers who have self perceptions around their driving and certain innate traits (selfishness, lack of concern for others) will prefer to buy cars that are advertised in a way that boosts their ego or enhances their self perception.

Or to quote an (Aussie) friend of mine "maybe not every BMW owner is an arsehole, but every arsehole I know owns a BMW "

Interesting (to me anyway) anecdotal aside, here in the UK it’s usually Audi drivers who are stereotyped as the aggressive drivers not so much Subaru WRX and BMW owners (source: reddit sub discussions and pub/work conversations, not scientific of course)