"doesn't make sense" is not a good way to evaluate statements if you don't have knowledge in the domain
I have a great deal of knowledge in the domain of the English language. "Health" can mean a lot of different things. Support of the survival and dominance of a species is a great indicator that the diet is "healthy".
flourished because agriculture supported a lot of people
All you have to do is to refer to modern organizations like the WHO to know that supporting life for a lot of people is a great deal of the meaning of "health".
I have a great deal of knowledge in the domain of the English language. "Health" can mean a lot of different things. Support of the survival and dominance of a species is a great indicator that the diet is "healthy".
flourished because agriculture supported a lot of people
All you have to do is to refer to modern organizations like the WHO to know that supporting life for a lot of people is a great deal of the meaning of "health".
[edit: clarity]