Actually, they did. NATO did not "force" the Yugoslav Army out of Kosovo, nor was the Kumanovo agreement a capitulation. That NATO and its press corps interpreted it that way and acted as if Serbia had unconditionally surrendered is a whole 'nother matter.
One could argue that NATO was cracking at the seams, that its escalated terror-bombing of civilian targets was a sign of desperation, and that had Serbia held out just a few more days... Well, it's not exactly clear what then. According to testimonies by Russian military and diplomats involved in the talks that resulted in the Kumanovo agreement, Moscow had caved in at the crucial time and accepted all of Washington's diktats. It is entirely possible the deal Milosevic thought he was getting sounded a lot better than what actually happened. Compared to NATO's demands in Rambouillet and at the start of the war, the Kumanovo MTA and UNSCR 1244 could technically be seen as victories for Serbia. The "only" trouble is that NATO had no intention of honoring the deal. Russian paratroopers were supposed to be a check on that; sadly, for whatever reason, Moscow failed to deploy them in force. (I have a theory that these two failures of the Yeltsin regime are what eventually brought it down, and represent a powerful motivator to the current Kremlin leadership not to screw the Serbs).
Back to Ambassador Jayatilleka:
"The...independence of Kosovo is the result of the failure of political will on the part of the ex-Yugoslav leadership," he wrote in a Sri Lankan newspaper, drawing lessons for his own country, where government forces are launching an assault into rebel territory where Tamil Tigers run a de facto state.
"Never withdraw the armed forces from any part of territory in which they are challenged, and never permit a foreign presence on (your) soil."
Hindsight or not, that ought to be elementary logic.
As I've pointed out before, any time the Serbs made any sort of deal with the EU, UN or NATO, they ended up being double-crossed: the Vance Plan, Dayton, the Kumanovo MTA. But of course, it was always the Serbs being accused of "negotiating in bad faith." Classic switcheroo.
It is clear that the assumption of bad faith has to be made in any dealings with the countries that recognized "Kosova." Anything short of that would be criminally stupid.