They made one big mistake in the middle of the century. Since then, they have been trying to put it right. When the Consumers Association recently published a review of healthy eating recommendations from 100 leading health authorities in countries like Britain, the USA and Australia, they found they all agreed on the need to shift away from animals and towards plants. Despite this there is confusion and not all of it accidental. When a poor and unreliable piece of research, often paid for by a company selling animal products, suggests the opposite, that's the one that makes the news.
Food is a very political issue.
Big companies make huge amounts of money from animal products and wield enormous power - so governments are not very willing to challenge them. There isn't the political will to change the national diet even though the World Health Organisation says that's what urgently needs to happen. From very earliest times right up to the middle of this century, the vast majority of people obtained most of their food from roots, fruits, vegetables, cereals and other plants. Leading authorities such as the World Health Organisation confirm this. Over millions of years, human beings have evolved to eat plant foods - we are naturally vegetarians.