But someone in the creative meeting must have asked, "Hey, what if we made Tombstone really cool? What if we made him more of a Kingpin than the Kingpin?" And it stuck. Some credit should go to the voice actor. (I can't keep it straight if it was Keith David or Michael Richardson. Somebody, feel free to correct me.) He brought a gravitas that was necessary for us to take Tombstone seriously.
It was both actually. Keith was in the first episode and later ones had Kevin doing Tombstone. I can't remember if Keith did more than the first episode though.