I am not a psychologist, just a random person with an 🐘🎺 but...
I have read quite a few accounts of exchanges like this, and there seems to be a power dynamic undercurrent. I don't believe Musk is trying to optimize production or cut costs. I believe those are pretexts for exercising power over people more educated, intelligent, and capable.
I believe the entire point of almost all of his interactions with engineers is, "You may think you're smart, but I'm the boss."