We learn in Gemarrah Yoma on daf lamed ches, amed bays, that one should not give a child the name of a rasha. Why then, did Korach’s parents give him his name, since "Korach" was the name of one of Esav’s children?

Fascinating question. Possibly there were other people named Korach who were not wicked. However, it may help to think about the meaning of the name. The root k-r-ch is used in the word "kereach" (bald) and "kerach" (ice). Apparently, ice is called kerach because it is smooth, like the bald head. Maybe smoothness is an idea that Korach's parents wanted to hope for, that things would be smooth for him, that he would not face hardship or strife. Possibly the inability to deal with situations that are not smooth is thge root od the dissappointment that led to Korach's downfall.