State-sponsored hackers are not going to ignore the opportunity. They probably have the capability already, in dozens of countries, and are just waiting for orders from the leaders. If war is starting, the order will be given. Sanctions could be enough to trigger it.
I could see arguing with the inevitability of the exploit -- Win95 botnets seemed much more inevitable to me than this Tesla mothership threat does. But it seems like you're arguing that they will both have similar impact if exploited. That doesn't make sense to me, because they're completely different threats, but it's possible I'm misunderstanding your argument in some way.
Imagine even 0.1% cars being controlled, the mayhem and loss of life that they can cause is just immense.
Power plants are also dangerous targets in a similar sense, but hopefully there is network separation for control services.