Hawaii already had a very low number of uninsured. They passed a law in 1974 requiring employers to provide coverage. Divide the huge costs of building the exchange into the relatively small number of uninsured and the cost per policy sold was approaching $20K. Literally a solution in search of a problem.
Hawaii’s 1974 law required employers to pay for part of the health insurance of employees who worked over 20 hours per week (no matter the number of employees). As a result, there were many people with 2 or more >20/hours per week jobs ... and no employer paid health insurance.
The people who came up with O-care only had to study Hawaii’s plan to see what would happen.
I’m not sure how they meshed Hawaii’s plan with the O-care plan which requires employers to provide health insurance to people who work over 30 hours per week (but only applies to 50 or more employees). Seems like that would be a mess to sort out.
More likely is that Obama needed Hawaii to set up a state exchange to counter the optics of the Republican states that opted out.
It may be as you say that Hawaii didn't need it, but Obama desperately needed his home state to not reject it.
-PJ