Could you tell me why was thyroid cancer prevalant among the population that was exposed to radiation from the chernobyl disaster?

Radioactive iodine: A low level of radioactive iodine was released during the chernobyl meltdown. Both normal and radioactive iodine collect in the thyroid. Particularly for children in that area at that time, there has been a small but significant increase in the development of thyroid cancer. Interestingly, after thyroid surgery, the most common therapy to cure thyroid cancer is a strong dose of radioactive iodine.

"Hot" iodine: Radioactive iodine was released from the nuclear reaction at Chernobyl. This was taken up by folks' thyroid glands and has caused a fair number of cancers but very few of these have proved fatal. They're quite low-grade. "Green" agitprop claimed Chernobyl would cause / has caused huge numbers of deaths but mainstream science has found the impact on overall mortality to be very small.

Radioactive iodine: Chernobyl released high levels of radioactive iodine, which contaminated the pastures of grazing cows and>> into the milk supply. Iodine insufficiency was prevalent in the local population. The thyroid gland avidly takes up iodine which is needed to make thyroid hormone(thyroxin), even more so if it's iodine deficient. As of 2006 5,000 children had developed thyroid cancer according to the WHO.