Yes; many of the specific bases of support they pointed to had been debunked before they were publicized by, among others, UN weapons inspectors. While it's far from proof, that alone is reason to believe that they were knowingly fabricating their claims.
Some links: https://www.npr.org/2013/03/19/174708587/u-n-weapons-inspect... https://www.cnn.com/2013/10/30/world/meast/iraq-weapons-insp...
Here is something about the Iraq-Al Qaeda link they tried to proof.
https://en.wikipedia.org/wiki/Saddam_Hussein_and_al-Qaeda_li...
I don't know if Bush and friends really believed their claims but if you looked at it from a neutral point of view it was very clear that they had made up their minds to invade Iraq and desperately tried and failed to find evidence.