I'm sure you started this video the same way I did. I thought now that's a tough carpet to clean. I clean carpets professionally in Tampa FL, and I have come across several carpets that look as bad as this one. Super heavy soil on a shag like carpet. The trick is using the right type of solution and equipment to remove tough soil from a carpet that looks like it should be thrown out.
In this video they use the right type of carpet cleaning extractor. It's called a rotating extractor. I use one on every tough carpet cleaning job I do. It works harder at cleaning the carpet then 5 guys cleaning at the same time. In this video the carpet cleaners have amped up their cleaning power by increasing the heat and pressure of their cleaning solution. This makes for a tough carpet cleaner but it has some draw backs. it can easily over wet the carpet and make for very long dry times, even a couple days of drying. Carpets that stay wet for a longer period of time are at greater risk for mold and bacteria growth. That's why I don't recommend high pressure carpet cleaning.
Instead of high pressure I use a carbonated cleaning solution that has a lot more cleaning power than a typical steam cleaning solution. At Chem-Dry of Tampa FL our carbonated cleaning solution explodes the dirt off the surface of the fiber and leaves the carpet clean, fresh and practically dry.