They didn't laugh because they thought that the farming itself was funny. It was the dark black armor they were wearing, or better to call it poorly fitting robes maybe?
"I knew that they had made something from monster materials and tree sap to be able to help them resist the manas making lightning, but this is a little much." The masks, pants, boots, and shirts, not to mention gloves were all loose but clearly dense and heavy. Meaning that the movements and the way the farmers looked was overall too comical.
Their movements were more akin to children struggling to learn to walk. Some of them stumbled and fell from time to time. If the lightning boars were not as gentle as they were this would be an opportunity for them to attack.
