There's no denying that Lewis' 4'3 height is short (Peter Dinklage is 4'5) but Sammy Davis Jr's height was 5'5 and is double Lewis' height. Maybe he was still growing? Or was shortsploitiation just a thing?
The 70s and 80s were characterized by roles for black men that were particularly diminutive and emasculating. ABC made Webster because Gary Coleman was a star. White audiences wanted to see a harmless black child being raised by white people, where he would serve as a jovial little garden gnome with a quick pseudo-ebonic retort to the stodgy white culture, which they were all too happy to be a part of. On the other hand you had Bill Cosby, an upper class doctor who told everybody that race didn't actually exist and everything was fine, and then you had Jimmy Walker, a half-witted minstrel straight out of Song of the South.
Side note...I saw a doc in which Jimmy Walker explained that he chose to play the character that way, and some of the other cast members were rather annoyed at that.
There used to be a hilarious show about undead people working for Heaven to bring down "Fausts," or people who had made bargains with the devil called "G vs E" (Good vs Evil).
In one episode, they were doing a prisoner swap, handing over one of Hell's biggest big-bads: Emmanuel Lewis. It wasn't him, but they had a young African-American kid mummified in heavy ropes so all you could see was the top of his head and his angry eyes.