For one thing, it's not Elon Musk's trucks, they're Tesla's. He doesn't own 100% of Tesla. His stake is about 22%.
Why did you think this had anything to do with self driving trucks? They're simply all electric semi's.
Self driving trucks are a lot further off than many speculators are suggesting. Even though the basic tech is already here. Real world use is a whole other thing. Who's going to control the load at each delivery stop?
As for these full electrics, they probably didn't think it through. Don't feeder trucks keep moving as needed? Sure they sit for some periods but they need to be readily available. No super chargers? So one trip, and it has to sit plugged in for 8 hours. Good one. LOL.