While I think there is some merit to what you're saying, you're forgetting two major diferences between driving am ICE car and an EV charged on fossil fuel electricity.

First, EV engines are far, far more energy efficient than ICEs. Secondly, fossil fuel power plants are far more efficient at converting fossil fuels to energy than ICEs are (since the energy efficiency of a thermal engine is proportional to its volume).

The result is that the EV car mileage you'll get by burning 1t of oil in an oil power plant is much, much higher than the mileage you'll get from that same 1t of oil in ICE cars. I'm not 100% sure if this holds true for coal based power plants, but those should be getting relatively rarer.

Not to mention, fossil fuel power plants can have much better filters and some CO2/CH4 capture technologies, so the mileage you get per ton of greenhouse gas emissions is even better than the energy per ton of fossil fuels.

I'll add that Hawaii currently generates 20%+ of their electricity from non-fossil fuels. Plus they are actively reducing fossil generation with a view to removing it completely.

Changes on this scale take time. But to make the islands much less dependent on fossil fuels, a two-pronged strategy is in play. Reduce fossil fuel generation, but also reduce the dependence on fossil fuel in transport.

As a long-term strategy, reducing the cost of importing all that fuel, over vast distances, seems to be a huge win for the islands. In every way (politically, economically, socially, environmentally) generating their own energy is a win.