Imagine a sports team in New York in 2001 with some sort of jihadist or mujahideen based name and the equivalent mujahideen imagery to what we see here.
There is no way that they would keep using that name.
The "Crusaders" was always a somewhat problematic name, but up until now it might have been fair to say that it didn't matter, because the crusades were ancient history and nothing to do with our country.
We can't say that now.
Before anyone complains about the 9/11 comparison, the loss of life per percentage of national population is similar and unlike 9/11 and the London terrorist bombings of 2005 (52 killed - not including the 4 bombers), the Christchurch shooter was aiming at a specific group of people, the same group that were the targeted by the crusades.