>>714570489
Martinet came up with the wacky wacky wahoo himself. Miyamoto liked it so much that they decided that was Mario back in the day.
Since then they've obviously turned that into the direction, and that's how they found a replacement that was suitable in Kevin Afghani, who despite everything still is pretty impressive for the fact that he can sound like Mario and his type of voice also fits with Luigi, Wario and Waluigi. Even if he's just an imitator I think he's a good replacement.