>>719722584
>Long standing villain
>Featured in many good games
>Aesthetically fits within the series
>Opinions on him are neutral at worst
These are all things Bowser has that Zavok does not
I guess they push the deadly six because they want some more villains that aren't Eggman or related to Eggman or something, and maybe Black Doom and his Black Bull and other such henchmen are too Shadow-specific.