There are two articles about the destruction of the Al Nuri Mosque in Mosul. The NY Times calls it “Another Loss for Mosul” (see: http://nyti.ms/2sVnSL8, which is a photo source) and Task & Purpose, one of my favorite military sources, calls it “ISIS Just Rage – Quit The Siege of Mosul ….” (see: http://bit.ly/2rGIrI3, which is also a photo source.)
Both articles agree that the Mosque was a center of gravity the center of the purported Daesh Caliphate.The Times provides a lot of information about the history and influence of the Mosque over time.
Task & Purpose goes into more detail from a tactical perspective and addresses the ISIS claim that the mosque was destroyed by an allied airstrike.
From my perspective, Symbolism and PSYOP are not lost on ISIS. Time and again they have proven that they understand the influence game. By blowing up the Mosque they deny the probable victors endless influence opportunities.
The Mosque has been prominent in Mosul for centuries and it is a revered and recognizable symbol. While in ISIS hands it served them well as a showcase while it was in their hands.
The destruction of the Mosque is another example of how ISIS routinely ignores rules of any kind, whether religious or secular or humanity, to further their own cause. Their track record of destroying religious artifacts is well known with the Mosque being only the latest example.
Even when people see through the shallow ISIS claim that the Mosque was destroyed by an air strike is proven false; the victors will not be able to use the ancient Mosque as a platform to proclaim their victory and the righteousness of their cause.