I had a knee jerk reaction to this but taking the high road. I sincerely don't believe that the venn diagram of people with security clearance doesn't overlap at all with "those that use illegal drugs"

I would guess that there's a culture of delusion surrounding this wherein because "it's the rules" they are actually followed. You know because rules are rules. The world, especially those like the Elons of the world, don't care to follow them as diligently as perhaps a command and control military / public service style structure demands. I'd even be surprised if even in the federal government those with security clearance were completely sober and free of the drugs considered illegal under US law.

You know Elon is gonna do what he wants to do. For better (electric cars, reusable rockets) or for worse (open his twitter feed any day of the week).