You know who else uses a lot of ketamine? The rave scene, the queer scene, and people treating PTSD. And those are some of the most un-Nazi folks out there.
It's a dissociative drug. It can be used recreationally, it can be used therapeutically, and of course, for medical purposes.
Let's be real. Why is Musk a megalomaniac? Because he is a megalomaniac. The end.
I think many of us see the the through line in Musk's story the same way we can see how our friends who spiraled into chaos and self-destruction had always been fragile or angry or hurt or whatever, but for others who were never perceptive or open enough to have seen the already-troubled side of these people, a drug abuse narrative (which often can have truth to it) can help it all become less bewildering.
Why, how, and when did he become a megalomaniac? Was he always this way? Did he start believing his own press at some point?
Body chemistry can affect how one cognates, perceives the world, and reacts to external (and internal) events. Half the world's population undergoes such effects naturally throughout their life:
* https://en.wikipedia.org/wiki/The_Female_Brain_(book)
It would not be surprising if folks who alter their brain chemistry without medical supervision may have their (perception of) reality changed due to it.