One way to tell if someone is smarter than you is if they are continually taking actions that appear stupid to you, yet which keep working out for them for reasons that appear like luck.
I think we can confidently call stupid actions stupid actions. Inertia from prior success can keep them from being company-ending actions, especially if they can be corrected once they are recognized as stupid (or once the people who knew they were stupid from the beginning can gather enough political clout).
Tesla has smart people, just like any tech company, but they're not uniquely smart and they're not immune to the same short-sighted thinking that plagues other tech companies.
Note that I think this particular idea is not necessarily bad for the company, it's just not anything special. It's basically Folding@Home, monetized. If you can convince enough people to leave it on (or force it on and somehow avoid legal/PR issues) then I guess you can save a tiny bit of money on certain kinds of workloads.
Could be. Even if few of Musk's decisions make sense to me, he has proven a lot of people wrong in the past, so I'll give him the benefit of the doubt.