At least in imagination we might conceive of a being who throughout his wandering in saṃsāra simply never acquired merit of the kind that would be a cause for his encountering a buddhasāsanā. Is there really any principle of Dhamma that would logically rule out the possibility of such a being? I don’t myself see one.
Perhaps in the Ājīvaka system saṃsāra wasn’t considered to be beginningless. At least that’s the only way I can see that followers of Makkhali might escape the charge that their teacher’s doctrine is falsified by the fact that dukkha isn’t yet universally extinguished.