Or the Iraqi (?) 'fighters' who dropped their AKs and ran away? Those were freebies to the jihadists. Tanks too. Gratis.
I don't know what the tank equivalent of scuttling is but they were too panicked (you're in a tank, ffś) or hurried to damage them properly. Or maybe it was pre-meditated treachery, by sympathisers?
Arms manufacturers might claim to be blameless and show you sales receipts detailing repectable non-terrorist *initial* buyers. It is the stuff that new sales are replacing which is the problem. Second-hand sales are out of the manufacturers control.
Victor Bout is in prison. He sold USSR army surplus in African countries. Some of those may have changed hands and served everyone from Boko Haram to Somali pirates to middle east jihadists. It's not easy to come by an aircraft fleet as cheaply as he did (corrupt post-Soviet officials) so it is not as if some other crook can easily take his place. Struggling air-cargo outfits do exist though. Scope for shady ops there, you'd think.