You’d think those giant loop videos would be taking up far more space

Someone above posted an article saying they aren't actually. But you'd be surprised at how little space those 10 hour videos can actually take. They're highly compressible since they're just the same still image and the same audio on repeat. A good compression algorithm (which Google certainly is using) would basically compress it into one instance of the song and how many times to repeat it (more complex than that, but that's the idea)