The SCOTUS found it in two 1937 cases that the Preamble’s “Promote the General Welfare phrase” allowed the Constitution with Congressional Acts with the Presidential approval to do almost anything that “promoted the general welfare.” Once that horse was out of the stall and escaped the barn, everything “promoted the general welfare” including anything an imaginative leftist could come up with that benefited anyone any where or the government or the state, or an imaginary benefit could be justified. It first of all found that Social Security taxes and payments promoted the general welfare.
The Constitution now says whatever any 5 out of 9 Supreme Court Justices want it to say at any point in time. Of course, one problem with having an all-powerful oligarchy of Justices writing and rewriting the Constitution is that another 5 out of 9 Justices can always decide that the Constitution says something different.