The typical evolution of the business process starts when a non-expert has to do a task based on secondhand knowledge from an expert. When that task or similar task is repeated then that process will be used again as it becomes embedded into the organisation. The five monkeys and banana experiment is s a good illustration of ‘how we do things here’ evolves. (By the way, there is dispute whether this experiment ever happened . See here for a discussion. Even if it didn’t, my own experience in organisations confirms that this is typical.)
If there are any variations to the requirements, the process will be modified but this variation is often not documented.
When another person performs that process or variants then again, yet another version of that process will evolve. So whilst the original process maybe documented, and parents that come after it are often undocumented and unknown.
Processes cannot be managed to become agile if they are unknown and tangled.