Other main suspects are obesity, poor choice of diet, and I believe a few other things. They probably all contribute somewhat.

It's also possible that the chemicals have something to do with some of the other contributions.

For instance, the rise in obesity rates over the last few decades isn't just a human thing. I've seen some research that found that animals are getting fatter, too. This includes lab animals that are fed controlled diets, so it isn't just that fat humans are eating more, and so also have more scraps to toss to the pets.

This suggests some sort of hormonal change or disruption might be a significant factor in rising obesity, and when you look for candidate hormonal disruption sources that both humans and animals would be exposed to, those "forever chemicals" are going to be at the top of the list.