They are mostly minimum-wageish workers who can't afford insurance on their own
Those numbers don't jibe: Minimum wage for full-time single employees is is $14,500 per year. The Medicaid income limit is $16,643 for single men. Every minimum wage worker should be covered by Medicaid, even in states that have not expanded coverage.
There is a hole in states that have not expanded Medicaid up to the bottom limit for ACA. Those people get no Medicaid and no ACA assistance. I actually had to take some 401K money as income to reach the bottom of the ACA limit when I first retired. Then my wife and I got a total refund of everything we paid into ACA for the year.