By insight, by practising introspection, or simply by experience. There are kinds of ignorance we have ended via experience. When we were a baby, we did not know fire burns or hurts. By touching fire, we soon learned it burnt. The Buddha taught ignorance does not have a cause (hetu) but taught it has food (ahara), namely, the five hindrances. When the five hindrances remain in the mind, ignorance receives support. But when the five hindrances are overcome, clarity of mind can manifest to end ignorance. Kind regards