you could argue afghanistan was a stable country under the Taliban. Abhorrent maybe, but for the layperson in the street, arguably more stable than it is now.
Yes, you certainly could argue that. However, I think that's largely down to
how the war has been conducted and managed rather thay
why it was waged in the first place.
I donīt remember Afghanistan being involved in 9/11 at all
You answer yourself HD in quoting my reference to al Qaeda's relationship with the Taliban directly beneath. I see what you're saying about invading Russia and Italy to get at criminal gangs operating in those countries. You could put the same argument about the UK invading Ireland to get at the IRA.
However, I feel your analogy is flawed. Let's be clear - al Qaeda were not operating in Afghanistan in defiance of the Taliban's wishes (as is the case with the examples you cite), but were there as the Taliban's guests.
Afghanistan under the Taliban was internationally recognised as a failed / pariah state (in much the same way as Somalia is now). This is the reason why there was a concerted campaign to stop the Taliban taking up Afghanistan's seat at the UN pre-2001. In such cases, you cannot enter into inter-governmental judicial treaties that cover extradition and the like. The only alternative was to go in and flush them out ourselves.