R. Mordechai Willig, in this week's TorahWeb essay, states -- as I've written here before -- that it is traditional for Jews to react to a tragedy with introspection and search for the sins that led to the unfortunate situation. Citing the opposition to the Rambam that past authorities claimed was the cause for the burning of the Talmud in 1242 and
the lack of synagogue decorum that the Tosafos Yom Tov suggested was the cause of the Takh Ve-Tat pogroms the Tosafos Yom Tov's attempt to reform synagogue decorum in the wake of the Takh Ve-Tat pogroms, R. Willig suggests that these two issues -- "Greater respect for opposing philosophies and the sanctity of the shul" -- are still areas in which we have room for improvement.
He further adds that "[s]pecial emphasis must be placed on interpersonal relationships" and "[o]ur war effort must include greater devotion to Torah study as well."
The first Mikdash was destroyed because we forsook Hashem’s Torah, the ultimate truth (Yirmiyahu 9:12, haftorah of Tisha B’av). The second Mikdash was destroyed because of baseless hatred, the opposite of peace. Only by correcting both of these errors can we merit the rebuilding of the Mikdash.