You put a group of people together and give them a common goal and magic can happen. Even if that magic, in this case, is just building a barn. It's hypnotic to see the organisation in this, like seeing a bunch of worker ants swarm together with one mind.
Penny Miller, the person who filmed the time lapse, writes:
I shot this video with my Canon 60d Camera using a Pixel TW-282/E3 Wireless remote timer set at 20 second intervals. I shot 1600 pictures from 7:00am until 5:00pm and compressed the 10 hours into 3 minutes and 30 seconds.