In my mind, the main difference is that they thought Iraq was working on the technology, not that they had it. If it’s being developed but it’s not complete, the superpower can basically wrestle their way in and go “no you fucking don’t” like an older brother ripping your favorite snack from your hands.
Meanwhile, we know damned well Russia already has assembled WMDs, that are presently sitting on ICBM rockets, with navigation targets pointed at American cities, that can be armed and fired within minutes of the order being given.
The same way the USA does (just for… Non American targets).
The whole WMDs in Iraq thing was basically international bullying.