Allama Iqbal didn't believe in Imam Mahdi????? Are you serious? Mate, you don't know anything then. Ibn e Khuldun was a historian of lesser credibility as in his muqaddimah, he has clearly stated that he has quoted all that he had heard without verifying it. Sindhi was no freedom fighter as well, lets not pull more history into it or there would be chapters of what he actually did to Muslims.
Good one mate. The reason behind negating Imam's A.S existence is to negate the reason for jihad as ghamdi clearly said that there were requirements and status of jihad that was analysed by Muhammad pbuh and after visaal, who has the authority to ascertain the same reasons and status. This happens when a person starts using more of intellect and relies on it than being humble and seeking guidance from Allah.