Because it does not matter to anybody. Saddam didn't have the WMDs, the evidence was manufactured. Did that fundamentally change anything with regards to the trustworthiness of US government & media when they claim some middle eastern country is developing/using WMDs?
On the international level, power matters. Political power, military power, economic power, not your reputation.
> politics or diplomacy based primarily on considerations of given circumstances and factors, rather than explicit ideological notions or moral and ethical premises
When was the last time that US used the WMDs excuse to drag allies into war?
It's always funny when we ignore the mass murderer in the room and instead focus on China's quite measured response to crime.
Very few people in international circles, especially those familiar with the Middle East believed it, which, unlike the 1st Gulf War, saw almost no support from our traditional allies.
The US media did a poor job of questioning the evidence. Late Night comedy probably did a better job - especially, questioning why so few allies were coming along for the ride.
For many people, it was around this time when they started trusting The Daily Show on Comedy Central more than they trusted Fox or CNN for their daily news.