Basically, they couldn't do anything without the US leadership, and for this very reason the US restrained from any decisive action until the self-inflicted damage to the EU was such that a common military policy became totally unthinkable for many years to come.

This is the most common conspiracy theory in Russia as well. With an occasional extra twist that it would have been impossible to contemplate Euro (and EMU before that) as the world's reserve currency while a war was going on in Europe's backyard, and so not doing everything possible was a smart thing to do for the USA. Recognising Kosovo is another match going into the same fire.