The survey isn’t about the “niche” subset of the population that is religious. It is about the composition of the entire population. Not a subset of the population so that isn’t relevant.
Edit: to be clear, I understand that there may be some niche subsets within this survey that may not be represented because there are only 20 people in the US that believe in that weird religion, but again, that has nothing to do with the larger, non-niche subsets which are absolutely represented with enough accuracy to draw statically significant conclusions with a sample size of 1000
The survey isn’t about the “niche” subset of the population that is religious. It is about the composition of the entire population. Not a subset of the population so that isn’t relevant.
Edit: to be clear, I understand that there may be some niche subsets within this survey that may not be represented because there are only 20 people in the US that believe in that weird religion, but again, that has nothing to do with the larger, non-niche subsets which are absolutely represented with enough accuracy to draw statically significant conclusions with a sample size of 1000