From the perspective of cold calculation, it was still only a couple of years after the fall of the USSR. The idea of a widespread war in SE Europe was problematic. Initially, NATO sat on the sidelines and gave the Euros a chance to deal with it. Lacking any real recent experience in matters of war, the Euros failed. NATO had to step in. Now, on the matter of what happened next, there is plenty of criticism to go around. A topic for another day ....
In the book "While America Sleeps" by Kagan and Kagan is a good analysis of the issue.
"NATO"? "Euros" were in NATO. Either way "Euros" negotiated Lisbon Agreement which was going to bring peace.