It is not necessarily always a deliberate Evil. Case in point: A book, originally written in the early 60's refers to the existence of bats, on an island. Encyclopedia Brittanica referred to said book, stating that bats existed. Fast forward 40 years. The bats are now no longer present on the island; their habitats destroyed, and unable to cope with introduced species (rats and cats). But no amount of convincing by a layperson could get EB to remove the reference to their existence, because that is confirmed in a published book, and there of course was never any funding to provide for repeated searches for an animal over several years time, which would be necessary in order to get the animal declared officially extinct. Without a published volume declaring the animal extinct, academia refused to acknowledge the reality, even though no one living on the island could remember having seen a bat for 40 near on years. Academia is very, very concerned with what can be proven, and referred to by other literature / sources. Hearsay doesn't cut it. Memory both fades and is embellished. Another case: Not so today, but previously in the not to distant past, children borne out of wedlock were a huge scandal. Such things could turn an entire family into social pariahs. Therefore, many families could go to quite extreme lengths to hide facts from not only society in general, but even their own family members. In many countries, as things were only written on paper, often by the clergy or doctor. If you had a doctor or minister sympathetic to your plight, or the wealth to bribe, and the ability to travel elsewhere for the delivery, then with a pen stroke, the blemish could be made to disappear. When an estimated 7% of all people in Britain today do not have the biological father they believe they have, it certainly puts a wrinkle in ancestry research.... There are many reasons why someone would "allow" the "official" history to change. Kind of frustrating for those that follow afterwards, attempting to reconstruct events.