The Narrator didn’t say that Roller Derby “became” a full contact sport in 1960, he said that “by” 1960 Roller Derby “evolves” into a full contact sport WITH a scoring system and bone rattling hits.
And saying that “Roller Derby rolls into the history books” is just a dramatic way of saying that popularity and interest in the sport pretty much disappeared. It doesn’t literally mean that every single person in the world stopped participating in, or even spectating at, the sport.
If people made movies that read like History books then most people wouldn’t watch them. There is no reason to be critical of a move when they haven’t done anything wrong.