I've been several times in the church in question (Cathedral of Christ the Savior in Moscow). It took 47 years to build (1836-1883), like many other major cathedrals around the world. It could easily hold 10,000 to 20,000 people standing inside (no seats, of course). And our services last at least 2 hours.
It was built to honor the memory of those who fell defending Christian civilization against Napoleon in the War of 1812, and in fact Tchaikovsky's 1812 Overture was written to be premiered for the dedication of the church.
As a symbol of the religious spirit of the nation, it stood a short distance from the Kremlin, which itself has some amazing churches dating from the late 1400s. It was destroyed in 1931 on order of Stalin (non-Russian, atheist) because of his hatred of Orthodox Christianity and of the Russian nation.
After being rebuilt 1995-2000, it has been the visible symbol of a resurgent Russian Orthodox Church which has over 100,000,000 adherents, and there have been several instances when religious processions numbering 250,000 have started from the grounds.
This whole performance and uproar is not just 3 innocent young women expressing their opinion and being unjustly persecuted. It is the deliberate introduction of demonic forces into a sacred space for the purpose of harming the spiritual peace of a sanctuary. Just as Stalin destroyed its "body" in 1931, these people wish to destroy its "soul".
Thank you for the inside story.