Tolstoy tries to make the point that it is not just leaders such as Napoleon that cause events, but all people involved, including the citizens of the countries. And yet, what causes them to behave as they do? Tolstoy gets into a discussion of human free will vs. inevitability, but this is a question with which many minds have struggled. Who really knows?
Ironically, though modernists want to explain all things by science, Christian evangelists fight in a war of the spiritual kind. This is vividly described by the Apostle Paul in Ephesians 6:12:
12 For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.
Anyone who misses this aspect of our lives cannot adequately, even by human standards, understand why things happen as they do. The real goal for us as Christians is, with the help of the Holy Spirit, to lead people to Christ that they may believe He is our Savior. The evil elements resist this in any way they can.
I try to pray for Christian evangelists, which is to say Christians, every day. I pray for wisdom and strength for us, understanding, knowledge and courage, and in general all that we need for the task. Though we are all given different gifts, I believe we all as a body are called by God to evangelize. I pray we do so as well as we can.