Listen, if they had intentionally distorted, as you seem to be intimating, why didn't they just go all the way and plant the WMD's to begin with?
Because they genuinely and sincerely BELIEVED that Iraq had WMD. They didn't KNOW it. They didn't have anything like conclusive proof. But they thought that once they went in and took over the country they would find them.
In other words, the play their hunches rather than the evidence. That's not exactly lying. They didn't say what they knew to be false. They said what they believed to be true. But they pretended to KNOW it rather than to merely BELIEVE it.