It is not, not at all. For example, there are many testimonies of the victims of the Holocaust or the Japanese victims of atomic war, and these accounts have been examined more than accounts of the victors.

"Winners write history" applies only to the old days when, if a nation was conquered, their culture was destroyed and all their documents were destroyed.
"The destruction of all records" would be a simple matter to have been burned a few books, and some monuments destroyed. Today, the destruction of a culture is much more difficult. Therefore, we have many, many accounts of the history of sacrifice.