Just for the record: of course large parts of it were manufactured. Some of it was manufactured by a so-called "source", but that source was so in-/non-credible that you wouldn't buy a used hammer from him, never mind a used car. And it was well known that this source was completely non-credible.
In addition, various other bits were combined in ways that the appearance of a threat was manufactured out of pieces of information that both weren't threatening in themselves and also did not constitute a real threat when combined appropriately (the infamous 45 minute claim is among these). For more, see the various UK inquiries regarding "intelligence failures" leading up to the Iraq war.
The difference between that and manufacturing the whole thing from scratch is at best marginal.