Great companies are defined by their ability to change. Apple changed when they re-hired Steve Jobs. Microsoft changed when they embraced open-source software. Amazon changed when they started selling groceries, and then cloud computing, and then original TV shows.
It is easy to imagine these changes as grand strategic moves, carefully planned and executed by a handful of luminaries. But lasting, meaningful change comes from many small, focused improvements over time. With patience, just one person can make a substantial impact in even the largest organizations.