Monumental events tend to involve a lot of unnamed people and tend to be larger than any one person's ambitions. However, movies are about characters. Writers/directors know that getting the audience to relate with just one character is more effective than just offering a statistical view. People have egos and the viewer wants to relate a historical event with their own lives.
The Imitation Game showed one man overcoming the stigmas of Aspergers and homosexuality saving the world with one machine (when, in real life, Britain had dozens of those machine and far more employees working on them). Frost/Nixon portrayed Nixon's public confession as an act of one journalist making an emotional breakthrough to the former president rather than it simply being a planned move from Nixon to improve his public image.
The Imitation Game showed one man overcoming the stigmas of Aspergers and homosexuality saving the world with one machine (when, in real life, Britain had dozens of those machine and far more employees working on them). Frost/Nixon portrayed Nixon's public confession as an act of one journalist making an emotional breakthrough to the former president rather than it simply being a planned move from Nixon to improve his public image.