Those reimbursements for deductibles and co-pays, for insurance company subsidies, and for the expanded Medicaid program, weren't part of the ACA and were never approved by Congress.  The basic subsidy for Medicaid expansion was only through 2016; the ACA law said they would phase out beginning 2017 (after Obama left office), so it was written to fail.  What the Obama Administration spent on subsidies was illegal.  Trump is just following the law as written.

The reason several states chose not to expand Mediciad to 400% of the poverty line was because it was written into the law that the cost would eventually have to be born by the states.  It was right there in black and white.