Tesla is not a "darling of the stock market".

You can find many articles referring to Tesla as a darling, though admittedly recently most articles are discussing if Tesla has lost that title. Lets just agree to disagree for the time being.

I'm not sure what you mean about changing the world.
It was mostly hyperbole, but not entirely. Tesla has inarguably rekindled the EV flame, which in turn is changing the world. Electric semi trucks could just be another step Tesla took that was bigger than the competitors.
Personally, I'm excited to get to the point where Tesla can make even just 10K or 20K a year and we start to see them on the road everywhere.
Yes. I think Tesla will have a significant edge in manufacturing electric semis over its competition for a long time, depending on demand.