Yes a huge number of the signups were eligible after Obamacare changed the eligibility rules and if their state agreed to the new lower eligibility requirements (about half the States didn’t)
But they weren’t eligible before. Before Obamacare you had to be not only very poor with no assets, you also had to be either pregnant or single mother with children under 5 or be poor and profoundly disabled.
Under the new Obamacare Medicaid expansion, you only have to have a low income. That’s it.
That’s how they are getting so many “newly insured”.
These people were signing up under old rules, not the new ACA.