The big problem we have with renewables right now is matching generation with demand. Solar is really cheap for daytime generation, but what are you going to do at night?
Electric cars don't have that problem. They're parked for most of the day, they need to be charged once a day or less, so they can be charged whenever renewable generation is available. Which makes deployment of renewables more economical, which means we get more of it.
> If we were rational and serious about making the biggest impact, we would reduce car dependency so the green electricity we generate can go to less wasteful means.
We can do two things at once.
The biggest thing we can do to reduce vehicle miles traveled is to relax zoning near urban areas to allow higher density housing to be built closer to jobs. That works, it makes housing more affordable (which is independently good) and people waste less time commuting.
It also takes years before the new housing is actually built and even then doesn't solve the entire problem. You can't replace last mile truck deliveries with higher density housing or mass transit; you need electric trucks. Nobody is going to build low ridership mass transit to the low density suburbs that already exist, and they're not all going to cease to exist.
100% of cars are not going away anytime in the next century, but making the large majority of new cars electric is feasible within the next few years.
This is not a problem with a single solution. It's a problem with 100 solutions that each have a niche and you solve the problem best by deploying them all, each in the place where it makes the most sense.