How did the Messenger see people being tortured in Hell on the night of Al-Isra wal-Mi'raj, even though souls await the Day of Judgment for reckoning and punishment?

The Prophet, peace and blessings be upon him, saw people being tormented during the Mi'raj (Ascension) journey. This torment could either be a Barzakhi (interim state) torment in the graves, which Allah revealed to him, or it could be a depiction of the torment they will face in the Hellfire on the Day of Judgment.

Evidence for Barzakhi torment is found in the verse regarding the people of Pharaoh: "The Fire, they are exposed to it morning and evening," and in the eclipse hadith where the Prophet, peace and blessings be upon him, saw those being tormented in the Fire.

It is more likely that what the Prophet, peace and blessings be upon him, saw during the Mi'raj was torment in the Barzakh. Allah knows best the nature of that.