Anime continuity: It's clearly stated both in episode 37 and 38 of SmR. The Cold Sleep happened, everyone woke up in the 30th century thanks to the Silver Crystal and some people refused the new status quo, they declared a war/tried to topple an *absolute*forking*monarchy and lost the war. They refused to get cleansed and "had no choice" (literally quoting) but leaving Earth. There is no mention of religion reasons or whatsoever.
They still started a war before there was even a monarchy, that we don't know if it's absolute or not (we don't know
anything of the government other than they have a royal family), and rather than letting themselves being cleansed of evil magical influences (because we
see the cleansing, and it amounts to exactly that) they left in exile... And joined Wiseman, or let him join, in spite of him being a known
mass murderer and serial killer.
That was for their ancestors, Demando's generation had been heavily influenced by Wiseman... And their attack on Earth explicitely caused billions of casualties, their plan aimed to change the timeline (one of the most incredibly
stupid things a time traveler could do, something well known to the general public since Ray Bradbury's short story
A Sound of Thunder), and their leader's goal is quite explicitely to rape Neo Queen Serenity or, if he can't get her, her teenaged version.