Memory is an often-imprecise function of the mind. Much of how we remember something owes to the atmosphere of the environment in which it happened, in which we experienced it.
This is especially true of seeing performances live, whether they are athletic, artistic or a combination of both. A brilliant performance in a nearly empty, nearly silent venue often will become less than it was in our memory. The same performance before a cheering or applauding large crowd at a significant event often is remembered as more than it was.
Video allows us to test memory dispassionately against reality.