Counterfactual reasoning can be tricky. We do want electric vehicles to be manufactured instead of other kinds of vehicles, and they won't be if nobody buys them. So, maybe you're doing your bit to make sure they're successful, versus less efficient vehicles? If you buy used then you're accepting other people's decisions about which new cars should be successful.

On the other hand, maybe you're thinking the total number of cars to be manufactured should go down, and this will happen if people stop buying them.