Is a man who is considered the most knowledgeable among those present sinful if he does not step forward to lead the prayer, adhering to the hadith, "Flee from imamate"?

Leadership (Imamate) is a communal obligation (fard kifaya), and it can become an individual obligation (fard ayn) if there is no one else suitable for it. The hadith mentioned in the question has no basis, and it is refuted by the authentic hadith of Uthman ibn Abi al-As: "You are their Imam, and follow the example of the weakest among them." This contains proof of the permissibility of seeking leadership. Sheikh al-Islam Ibn Taymiyyah was asked whether leadership is better or leaving it is better, and he replied: "Rather, he should lead them in prayer, and he will be rewarded for it." Some scholars disliked leadership only because of the responsibility it entails. If there is someone among the people suitable for it, one should not rush into it. However, if there is no one suitable, there is no point in abandoning it.