While the extension only has one or two entry points for client-side code, it has many more modules registered internally. This is a left-over from how Wikibase misunderstood how modules wok in ResourceLoader.
These internal modules are all publicly registered via the JS-startup of all page views on Commons. This metadata has to download, parse, and execute before any interactive features can start to load.
Modules that are only references internally should be merged into the respective module bundles that are actual entry points, and/or in shared bundles used by multiple entry points.
More about this general issue at T202154. See also "Size of scripts" at https://www.mediawiki.org/wiki/Wikimedia_Performance_Team/Page_load_performance.