All of those unnamed sources are they fabrications or lies told by sources.
Since there are numerous instances in our recent history of so-called journalists being caught literally making up -- inventing -- stories, the likelihood that most "unnamed sources" are fabrications is very, very high.
It's a dirty and very convenient game the media plays. Over time they have managed to make the notion that they don't have to reveal sources pretty much unquestioned and unquestionable. Yet there is absolutely zero way anyone can independently verify that a source even exists in any given story. They now rely almost exclusively on anonymous sources in even relatively simple, non-political stories, all the while shielded by a complete misinterpretation of the First Amendment.
Congress shall make no law...abridging the freedom of speech, or of the press...
This simple, clear statement has been broadly over-interpreted to mean the media can do any damned thing it wants without accountability.