I think our carnivore and fiber friends need to find some common ground. Neither one is the enemy - there are much more important dietary problems …
I would wager to guess the high cost and recent perception of negative health/environmental outcomes of red meat likely contribute to the drop in red meat consumption.
I would separately guess the drop in fiber consumption could be linked inversely to the rise in consumption of processed foods + refined carbohydrates which have no or less fiber.
It’s becoming increasingly expensive to feed a family with red meat. I’m down to 15% red meat, 80% white meat, 2.5% eggs and 2.5% processed pork (sausage) to cook on the feijoada, monthly.
If I ditch the 15% of red meat I can increase the amount of white meat I buy in 40%.