The time lapse catches the strikes by chance. There are ~100 lightning flashes per second globally (80% are in-cloud flashes and 20% are cloud-to-ground flashes) and ~2000 thunderstorms occurring simultaneously on Earth. [1]
That's a huge opportunity to catch lightning flashes over a high quality time lapse from August to October 2011 (the time span of the video).
The astronauts' real-time views from the ISS' windows must be amazing. If I were up there in the ISS, I'd never get any work done because I'd be staring out the window the whole time!
