The reason you're doing better at fairs is simple. The customer can actually see, touch, and look at the quality of your work. Can't do that online.
Working a fair is simple. You dress nice, always stand up, and be ready to interact with your customer. And smile... a lot.
I have to respectfully disagree with Crafty Couple about the flyer and cards. You're there to sell today, and if the customer sees they can get it cheaper online with a discount, you just lost a cash sale. And isn't that why you're doing the fair in the first place?
I don't do fairs to drive traffic to my website. That's defeating the whole reason to do craft fairs. I have a section on my website that drives traffic to the shows. And I have a discount coupon the customer can print and give me at the show, not the other way around. Because the fairs are where the money is.
Now I exhibit with a pretty serious group of crafters. We do some serious shows just about every weekend during the season. Here's some photos from one promoter I do a number of shows with here in New England. https://castleberryfairs.com/gallery/
Some have canopies for outdoor shows that cost upwards of $1,000. They all have a web presence, but to a person they all will say they can make more in one weekend than they will do in a year online.