I'm not aware of Ukraine kicking out weapons inspectors from known previous WMD sites, or bluffing about having CBRN weapons. The invasion of Iraq was bumbling and based on piss-poor intelligence, but the belief in a threat wasn't groundless. https://www.csmonitor.com/layout/set/amphtml/World/Global-Ne...
The current Russian claims about Ukraine, however, do appear groundless, based on the consensus of international media.
The belief in a threat was manufactured by cherry-picking any weak scraps of intelligence that could be assembled into a believable marketing pitch for an invasion. Your average mouthbreathing intel analyst wouldn’t recommend invading a taco stand based on the shady sources and thin reporting used to justify this war.
Although I am certainly not well informed, as I could not predict this scale of military operation, I'd like to say that "consensus of international media" is not worth much at times of war. Because I feel like there is never a lot of disagreement in media during such crises. Maybe after, when the situation calmed.
The current Russian claims about Ukraine, however, do appear groundless, based on the consensus of international media.