So isn't the gun show at some fault here?
If their rules are that you need a FFL to sell guns, then WHY did this non-FFL have a table(setup) to sell at this gun show.
Why did they allow him there w/o a license?
As it was explained earlier, some gun shows use a central table for non-FFLs. However, in this case, the gun show promoter himself didn't know he was going to require all sales through FFLs until the Thursday before the show and he didn't notify his customers until they started showing up.
You can read more about that mess in these two posts:
Penny-wise and pound-foolish. The gun show promoter's greed in collecting the table fees from Copeland led to the show being kicked out of it's usual venue.
As discussed in the above links, this happened at the now infamous Boedeker gun show. The previous tenant had been the Saxet Gun Show (who was also the tenant when ATF got interested in the place to begin with), so Boedeker had been there only 4 months when this happened and may not have been aware of Mr. Copeland's history.