The essence of Shirley Warshaw's views is that President Nixon took up office with a strong commitment to cabinet government, especially concerning domestic matters, and then moved fairly rapidly to a centralized White House management structure. She concluded that cabinet government failed, caused largely by the president's lack of participation in domestic policy making.
Let me offer a variation on this theme. All presidents over the last few decades have entered office proclaiming their commitment to cabinet government. All soon change to one form or another of White House staff control--for very good and logical reasons.
Just a couple of quotes to set the stage.
Senator Muskie, before the 1968 Democratic convention, stated, "I recommend that the platform endorse the concept of more effective coordination of related federal activities through a strengthened Executive Office of the President." The Democratic platform adopted the sense of that proposal. This followed by two years the same senator's testimony before a Senate Committee, where he said, "The President needs a mechanism for domestic affairs comparable to that available in foreign affairs."
Hubert Humphrey, speaking in Los Angeles the October before the 1968 elections, stated, "a National Domestic Policy Council should be established to provide the same comprehensive analysis of domestic problems as the National Security Council."
So the issue of centralization was certainly "on the table" before President Nixon entered office.
Why do presidents run for, and take up, office supporting cabinet government? Why do they find it doesn't and can't work, and so change to a more workable system?
As to the first question, looking in from the outside it seems quite logical to have the secretary of HUD, for example, be responsible for housing policy development. Cabinet government is also seen as democratic, in contradistinction to "imperialistic," to be sharing power broadly among a group of executives. The public expects, and is comforted by, a collegial-like grouping of wise men taking care of their government even though they elect only one chief executive. The press supports that view, or certainly criticizes the reverse. Then, also, a department secretary's job is seen as one of considerable distinction and dignity. Those jobs are confirmed by the Senate. How could they possibly not be the vicars in their field? Then, to clinch it, the president is at the same time attempting to recruit candidates for his cabinet. He would like them to be perceived, and to perceive themselves, as very important people. So all the forces align to cause presidents to enter office proclaiming a policy of cabinet government. The die is set; they all start the same way.