What is the artstyle called where they have the protagonist large and all the other characters within the perimeter of the protagonist?
It's a form of hierarchical proportion:

Hierarchical proportion is a technique used in art, mostly in sculpture and painting, in which the artist uses unnatural proportion or scale to depict the relative importance of the figures in the artwork.
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Larger figures in these images play a larger role within the context, have a higher value or authority, are wealthier, more powerful, &amp;c.
It has been used throughout the history of the visual arts:
Well-known examples include religious depictions (e.g. Madonna with Child, the Last Judgment), societal depictions (where those with higher ranks or power are relatively larger, such as family group sculptures from ancient Egypt, or the donors of an artwork), depictions of royalty (think about Egyptian reliefs, or the Stele of Naram-Sin), and narratives (like posters of Star Wars).