I sold things at craft fairs for a few years, and while I did not get rich, I did make enough to cover the
mortgage on the farm in December/January (months we always had trouble with). When the US increased trade with China the craft market really suffered. Few people want to buy a $15 ornament when you can buy a 'prettier' version at your
local store for $5. If you do hit on an original idea that sells well, it will be copied en masse by the next fair.
If you do get into crafting, follow the rules of staging/marketing and become a good sales person. The key (for fairs where there are lots of booths) is having that stand out item that is not seen in every other booth, and pricing it right. To make it work, it has to be a business, know what I mean? The people who dabble never seem to do well. the people who think they can give 10% effort and get 100% return never seem to do well either.
It was great for me at the time because I had small children, and could work on crafts while they were asleep or playing. I also took them to shows more often than not. As soon as my kids got old enough so that they did not need constant tending, I headed outside! The craft volume dropped off sharply at that point