Prisoners may have been given an option of stay in the prison or we will give you a little bit of money and you go home. Nobody held a gun to their head and put them on a plane. They might not have liked the idea of being held in a prison or going home and they chose they decided they preferred to go home with a little bit of money in their pocket.
Shaffir to Herzog: Opposition failed to show leadership in political battles against PM (Haaretz)
from the article: Israel secretly repatriated 1,000 to Sudan, without informing UN