Avidyā is the source of the others, whether dormant, attenuated, interrupted, or active
This sutra establishes a key element to understand the theory of kleshas: all kleshas are generated by avidyā; and when coped with, they all conduct back to avidyā - 'thinking to know', 'illusory knowledge' or nescience. All kleshas are but varieties of nescience, because all of them are permeated by delusion. When an object is coloured by nescience, it is followed by the other kleshas. These are experienced whenever there is nescience and they dwindle away when nescience is attenuated. (Vyasa commentary on 2.4, Swami Hariharananda Aranya, Yoga philosophy of Patañjali, p.119)
The second essential notion given by this sutra is that the kleshas are embedded in the human condition. There is (almost) no way to delete them, but we can certainly render them infertile knowing that under specific circumstances, all kleshas can explode again, even if they have been latent for long periods of time. This is sharp alert to the sadhaka: kleshas do not disappear, the practitioner must always be alert and never stop practicing kriya yoga, which is the real antidote to the propagation of the Kleshas (Klesha-vrtti).
According to Patañjali, the kleshas can assume four states: dormant, attenuated, interrupted or active.
A klesha is at a dormant state when we cannot perceive it because the conditions are not proper to its manifestation. For example, we are always scared to die (abhinivesha) but not all our actions are driven by this fear. When we feel we are in a life threatening situation, then the klesha appears and drives us to action. By no mean the klesha was under control, it just needed the right stimulus to be activated.
The attenuated condition is that in which the klesha is present but in weak conditions. This is typical of the sadhaka with a long practice. He will still carry the burden of the kleshas, but their weight will be much lighter and easier to deal with.
When our mind is captured by a kleshas, the others are usually inactive. Patañjali calls this state 'interrupted' or 'alternating'. We are able to feel only one pain at a time. If for instance we suffer a headache and a stomachache, our brain will send the inputs of the two pains alternatively and not simultaneously, even when the series of pain inputs from the two sources are so close to each other to appear to be simultaneous.
Finally, the active state is the one characterized by no control. The ordinary situation of the human kind.
The practice of yoga not only does attenuate the states of affliction, it also allows the sadhaka achieve prasamkhyana or discriminative knowledge. Once the yogi has gained discriminative knowledge, and connected with the primary essence of reality and not its appearances; when a yogi reaches reality by humility and conscience of avidyā (of his nescience), then the klesha-mother, which is avidyā, dries up and becomes sterile. The seed of affliction will still be there, but it won’t be able to propagate anymore. The seeds of suffering will be then roasted in the fire of knowledge, which destroys their potency to sprout (G. Maehle, Ashtanga Yoga, p. 188).
This is might be the result of a long and uninterrupted practice of kriya yoga: burning the seeds of suffering, finding peace in the essence of reality, in its simplicity, in its infinite wisdom.