This is an interesting view from the article I linked: https://prophecycourse.org/session/more/man-of-sin/
"The man of sin is John of Gischala, a Jewish robber-baron turned Zealot leader. John fulfills Paul’s 2 Thessalonians 2 prophecy:
He was revealed during Israel’s Great Revolt, prior to the nation’s day of the Lord judgment in 70 AD.
He threw off the Mosaic Law, fueling a crime wave, famine and civil war throughout Jerusalem.
He positioned himself over all Israel as a despotic ruler, both symbolically and literally “taking his seat in the Temple of God,” exalting himself even over the Temple objects of worship.
He was “reduced to nothing” at the Lord’s coming in judgment over Israel by the hand of Rome.
A final word from Josephus:
“Yet did John [of Gischala] demonstrate by his actions that these Sicarii [of Masada] were more moderate than he was himself, for he not only slew all such as gave him good counsel to do what was right, but treated them worst of all, as the most bitter enemies that he had among all the Citizens; nay, he filled his entire country with ten thousand instances of wickedness, such as a man who was already hardened sufficiently in his impiety towards God would naturally do; for the food was unlawful that was set upon his table, and he rejected those purifications that the law of his country had ordained; so that it was no longer a wonder if he, who was so mad in his impiety towards God, did not observe any rules of gentleness and common affection towards men.” (Wars 7.8.1.)
In this talk, we established a basic foundation for the timing of this prophecy, covered the four different views on the son of perdition, and finally, we zeroed in on Josephus’ picture of utter lawlessness in Jerusalem during the Great Revolt of Judea. I believe, as a first-century Jewish eyewitness, Josephus is absolutely one of the best sources we have outside the Bible for understanding the trouble of those days. I believe the man of lawlessness was John of Gischala and I believe the historical account given to us by Josephus makes this clear."