"So it makes you feel fuller without adding calories, like GLP-1 drugs"
Nobody really knows how GLP-1 agonists work, but given the other effects (e.g. insulin stability, change in other addictive behaviours etc.) it's definitely not just this.
What are you talking about?? Meat contains no fiber. The primary fiber source is plant-based foods (e.g., vegetables). So modern populations eating lots of meat means they're getting little to no fiber.