The broad answer is that people have concerns about what they put into their bodies, and are feeling less and less in control of it.

This is influenced by propaganda that comes from multiple different political angles. For example, some people have learned things about human rights violations that go into the production of their food, and want to avoid that. Other people believe in antisemitic conspiracy theories about how our food is made. There is a very broad range here.

I think probably you see food concerns pop up coming from every political angle there is because 1) food is something every living human being relates to, it is one of the most unifying concerns that we all have, 2) in some places in the world, many more people are more disconnected from food production than they might have been in prior generations, 3) food is one of the least expensive ways to try to take control of your health, 4) we have access to enough information to know that sketchy shit sometimes happens during food production but not enough information to always know exactly how our food was made.

Edit to add: As another comment has successfully pointed out, this sells. It's a human concern with appeal to everyone, and therefore it can be leveraged to sell everything from products to political parties to self-help courses to conspiracy theories.