I have mixed feelings about Maggie, but I don't see a lot of evidence that she "sat on" news to advance her own career with her book. I think she was pretty dogged in reporting things about Trump as they happened and as she got them. People want to believe this about her -- that she put her own ambition ahead of her role as a journalist -- but there doesn't seem to be any evidence to support it that I have read. In fact, she released the tidbit about Pence refusing to get in the car with the Secret Service ahead of the publication of the book because she (or she and the Times editors) felt it was too newsworthy to sit on.
I don't know that I believe the Times should have granted her book leave to continue to gather more stuff. But that is how these things work. She would likely not work for the Times if they didn't allow her to work for CNN and also get a book advance, because they cannot pay her what she could likely command elsewhere. Jonathan Swan wrote a book about Trump and didn't get accused of withholding information for it, even though there was stuff in there that wasn't in his reporting for Axios. Jonathan Lemire did the same, even though the book had reporting in it that wasn't in Politico or the AP. Why do we think Maggie gets singled out so frequently by people who have never so much as covered a school board meeting?
Letting subject hang themselves with their own words is a tricky balancing act. I experienced it last year with Aaron Rodgers, and I had the same people who attack Haberman coming after me insisting that I was being a stenographer for Rodgers and that I should have been calling him out at every turn. I did fact check him and challenge him on some things where he was blatantly wrong, but I also don't know that it's a feature writer's job to play Issac Chotiner. To me, some of Rodgers' opinions revealed him to be exactly the internet-brained Rogan listener he clearly is, and it's more devastating to let the subject hang himself.
Trump has changed some of that calculus because of what's at stake and I did enjoy the part in Kruse's piece where Haberman tried to give the Times Washington Bureau a crash course in Trumpism and they scoffed, thinking they knew better. She does understand what a craven liar he is, and most of the press still struggles with grasping with his motivations, trying to assign reason to any of them.