Why did TV cartoons barely move, and how did that shape anime?

Because reusing drawings made television animation affordable, and it suited the small screen. Limited animation is a technique within traditional animation that reuses frames of character animation. The early animator Winsor McCay boasted that in Gertie the Dinosaur (1914) everything moved, including the rocks and blades of grass in the background; by 1918 his The Sinking of the Lusitania used cels over still backgrounds.

Television made the reuse routine. Because television screens were much smaller than theatre screens, limited animation, with its emphasis on character close-ups and dialogue-based humour, was a better fit for the more intimate home viewing experience, and its financial benefits led television animation companies to rely on it extensively. The numbers were tight: the first Charlie Brown special, A Charlie Brown Christmas, was given only a $76,000 budget and four months to produce 30 minutes of animation. One of the cheapest approaches, Syncro-Vox, superimposed film of the voice actor's moving lips over a still frame of the character.

In Japan the same squeeze became a style. Limited animation proved so popular there that the word anime entered English for the distinctive Japanese style. Osamu Tezuka's Astro Boy, first broadcast on New Year's Day 1963, cut costs to 2.5 million yen per episode with techniques such as shooting on threes, stop images, repetition, sectioning, combined use and short shots. None of these methods were invented by Tezuka's studio, but they were refined there, and later adopted by the television anime industry at large.