There are some scholars like the erudite Muaritanian Quran scholar who says Allah SWT is talking to the muslims here. And the first great mischief of Bani Israel was not the first and second temple but actually the mischief at the time of the Prophet PBUH. What greater mischief than that!
Allah SWT gave the muslims the victory at Khaiber and this was revealed after all that. Jews outnumbered muslim in Yathrib at one time eventually the muslims took over.
According to some historians it was 1/3 jewish at the time of muslims arrival.
The second mischief is about a future event yet to come in relation to the time of Prophet PBUH. Second mischief is now.m according to great Mauritanian
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