Yes, a vaccinated person who has a symptomatic breakthrough infection is contagious and can spread Covid just like an unvaccinated person. However, it is still a somewhat rare occurrence that a fully vaccinated person has a symptomatic breakthrough infection in the first place. The vaccine efficacy is still around 88% at preventing symptomatic infection (down from 95% in the original trial). So the more people you have vaccinated the less community spread you should have. My guess is similar to other parts of the country the overwhelming majority of infections in Hawaii are among the unvaccinated so their spread has little to do with breakthrough infections. They have a higher vaccination rate but not high enough to avoid community spread.
I think what we are learning with delta is that we need much higher levels of immunity due to the virus being more contagious. Hopefully the combination of full FDA approval in a few weeks along with the situation on the ground in places like FL and many large corporations starting to require vaccination will jump start the vaccination efforts. It would be great to see the US get to 80%+ fully vaccinated. I fear in some places that will never happen but they will eventually get to immunity the hard way