That's not entirely true. Everyone forgets there was an individual mandate penalty that his administration & congress repealed.
Anyone remember how the ACA assessed a tax on those who were not insured? (with income based exceptions). The tax was meant to feed into the ACA and keep plans in the marketplace cheaper, and to stop the program from adding to the federal deficit.
Once the trump administration came in they worked with Congress to eliminate that tax penalty.
Here is a helpful article that talks about the penalty and what the early findings showed when it was removed.