Time is a factor in whether a system of government or non-governance survives.Well, no case needs be made.
Anarchism is not about disorganisation. Quite the opposite, actually. An anarchist society is one which is run on democratic principles from the bottom-up - it is democratic all the way through. Local assemblies of people could then co-operate in ways they see fit with others, and send representatives to regional co-operative ventures.
Rojava is not running on a statist model. But they have been hands-down the most effective force in the regional arena in the fight against the Islamic State. So your hypothesis on defence doesn't really hold true.
Rojava has had a very short life. Its having recently popped into existence doesn't
mean that it will endure. Moreover, this does not debunk my claim that people tend
to form governments. Note that the vast majority of people around the world are
under the thumb of one or another. Some (eg, ours) have been around for centuries.
Others are more recent, but only as replacements for prior governments.
This discussion is analogous to arguments about the 2nd law of thermodynamics.
Some argue that it's possible for a closed system's entropy to increase because it
can happen briefly on a microscopic scale. But this isn't relevant in the real world
on a larger scale because the tendency for entropy to increase is overwhelming.
So we don't get to disobey the law of entropy in the larger real world.
And in that world, governments happen.
'One could also, in relation to that, look at the example of the anarchists in Spain during the Spanish Civil War. Having switched from capitalistic and statist systems of organising industry, agriculture, defence and so forth, productivity went through the roof! It was only because they were turned-on by other Republican factions that the war went to Franco.
I'm not familiar with agricultural economy of that time & place.
But I do know that Spain now has a government.