France is unwilling and not necessarily politically capable to handle such a mess, especially considering the growing political influence of its islamic minority. It would also be a perfect example of the mentioned scenarios where colonies aren't worth it for the colonizer, and France currently has plenty of issues with its "former" colony buddies in Africa already.
Ironically, USA could be interested, just like in many such cases the colonizers were, for geostrategic reasons (Middle East, Hezbollah central, do the math), but again, the legalities and politics would be incredibly nasty on the US side, and its also telling that this call was not extended to the USA.
Secondly, the idea of self-governance works well only in reasonably homogenous, or at least solidly dominated by a not too harsh national group.
Unfortunately Lebanon is a case of the opposite - a lot of the Shia would rather be ruled Iranian foreigners than their Chrisitian and Sunni "compatriots", and likewise, those would find more in common with foreigners who the Shia consider great enemies than with their Hezbollah supporting neighbors.
So, the what is the "self" in self-governance in such a case?
On a very conceptual level its just non applicable to such countries.
That's whatan empire is you extract wealth. Sometimes through directly taking it other times through tribute. This is how everyone from the akkadians to the Brits operated. The only thing the Euros did different was scale. Due to extreme tech disparity it's still just conquest.
Its less nukes, and more the economics and politics of it.
After all, nuclear powers would not be high on the list of potential colonisation targets. Countries that can't even put together half a functional armored division would be.
For western powers, the internal political factors combined with the high cost of using a modern army in the field to "win the peace" (see: Afghanistan) vs the potential benefits (resources which they may aswell get by paying local head honcho to have his semi-slave labor do it, or stand aside as western corporations do it) are the main showstopper.
For non-western medium powers, its the threat of military and non military intervention from western "international order" establishment and their local peers.
For non-western major powers, the western media and political establishment could annoy them somewhat with non-military interventions, but overall they are the ones doing it, "silently" for the sake of being left alone.