On the day of judgement why will people enter jahanam as nations with their leaders?

The Messenger (saw) warned of blindly following rulers, supporting them in their wrongdoings, resulting in separation from the messengeron that day: ‘After me there will come rulers who will lie and oppress. So anyone who upholds the untruths that they speak and assists in the wrong that they do will have no relationship with me, and I will have none with him; nor will that person pass by the pool of paradise.’ (Ahmad, Musnad, V, 191; Tirmidhi, Sunan, IV, 525) When the Messenger of God (saw) described tyrannical rulers, he did so in the following terms. ‘Whoever repudiates them will find deliverance, and whoever avoids them will be safe, or almost safe, and whoever falls in with them will be accounted as one of them’ ” (Hathami, Majmu‘ al-Zawa’id, V, 411; Tabarani, Al-Mu‘jam al Kabir, XI, 39) The leaders of a qawm (nation) in this world will be its leaders on the Day of Judgement. If they guided their people correctly in this world, under their banner they will march to jannah. If they misguided them, their followers will follow their march to jahanam. Take care of which leaders you follow and which societies you integrate into. And We did certainly send Moses with Our signs and a clear authority to Pharaoh and his establishment, but they followed the command of Pharaoh, and the command of Pharaoh was not [at all] discerning. He will precede his people on the Day of Resurrection and lead them into the Fire; and wretched is the place to which they are led. (Qur'an 11:97-99) The Prophet (peace be upon him) said: On the Day of Resurrection, the banner of the poets of ignorance will be in the hands of Imra-ul-Quais, and all of them will march towards Hell under his leadership.