Range: one of the biggest complaints people have about EVs is that you can't go very far without recharging (gasoline cars need to be "recharged", too, but for some reason we've all agreed to build gas stations at every other intersection to accomplish this feat). In Hawaii, though, except on the Big Island, range isn't really an issue. How far can you drive on Oahu before you start coming back? To go all the way around the island is farther than the 40-50 mile range of most EVs for sale today, but not a lot of people here drive from Honolulu to Turtle Bay and back every day. Those that do can stick with their gas burners, for most everyone else, EVs are ideal.
Target audience: Hawaii citizens are often at the forefront of ecological issues. And why shouldn't they be? The environment here is beautiful and nature is so much a part of one's daily life. From the ocean to the fresh air, the rocks to the deep valleys, people here are passionate about the ʻaina (loosely: the land) and the environment.
High energy costs: as I said, gas prices here are high. This is because almost every little bit needs to be transported here. Because gasoline costs an arm and a leg here, the cost difference to drive a standard gasoline car here versus on the mainland makes the EV's cost premium in Hawaii so much less of an issue, especially when you take solar energy into consideration.
Solar: the sun shines so much here, it's a crime there aren't solar panels atop every roof. Tesla Motors will offer a solar package with their Roadsters to make driving that speed demon net energy positive. Any electric car company that comes to Hawaii should do the same thing, because it's cool and because it's sensible. There are enough people with money here who would gladly buy an EV and a set of solar panels just so they never have to buy gas again. Trust me.
So, that's my reasoning. There are some groups here who are thinking the same thing. If I have time, I'll check up on them while I'm here and see how long it'll be before there's nothing but EVs here.