It's funny to me that the government was so intent on implementing a bunch of policies in the name of "efficiency" when DHS is a prime example of an inefficient

It's funny to me that the government was so intent on implementing a bunch of policies in the name of "efficiency" when DHS is a prime example of an inefficient agency. Why should we have an entire department dedicated to all the things it does when we could simply devolve many of the parts back to their original departments (INS back to DOJ, TSA back to DOT, etc), leaving a much more slimmed down entity (or perhaps none at all)?