well, not all stages of the history of wizarding world were mentioned.
as compared to the real world, you can find a lot of wars, events taking place in the past, but not everything was mentioned in text except those really big ones.
my idea was that we could come out with a world, entirely ours, without the reference of Voldemort, Dumbledore, Harry Potter.
and being an Order who was fighting against the corrupted Ministry, I'm sure the Ministry would like to downplay it