Strictly speaking, Tesla does not own its dealerships. Musk certainly could afford to buy private security (which btw, should become even more of a booming business... look for the stocks...) for them, which I'm sure he has considered. However, with effective law enforcement, that shouldn't be necessary.
As for Bondi and Kash, I'd say yes, it's a good use of their time. These are crimes, plain and simple. I don't expect much from the various levels of govt, but the one thing I think they should be able to do without fcuking it up, is domestic law and order.
But I think the real reason it's a good use of their time is that with even a bit of investigation, they should be able to find out if these attacks, particularly on the dealerships, are organized or not. If they can prove a connection to someone like Soros, it's definitely a great use of their time.