It's not just due to that, but it helps. Medicare is moving its reimbursement model from fee for service to fee for value. That means smaller players are more impacted than larger ones just by the volume of patients. Another factor is the move to outpatient. A lot of smaller hospitals didn't have the infrastructure for that or had to compete against established players. The push for electronic health records has raised IT costs for a lot of systems. They end up having to align with a big player and piggyback (eventually merging) or suffer with a scaled down version of software and limited access to things like reporting.
I don't really see it as a malicious intent of the ACA, but it's a byproduct that has smaller systems joining larger nonprofits. In Florida, 2 or 3 joined Cleveland Clinic, and at least one joined Baptist. I know HCA or Tenet picked up some too. One of the systems that joined Cleveland used to have a policy that if you were a member of the community, you'd get full treatment regardless of cost. A person living in poverty who got cancer would get the same treatment as a millionaire and the bill would be covered by charitable donations.