I forgot to mention that it is also necessary to set map._allowWheelToZoom = true; so that you can zoom with the mouse.

I noticed that the npm library "apple-mapkit-js" is no longer maintained and also not an official release from Apple. Therefore the updates of the past two years are not available (including the mousewheel scrolling). Instead you should load the library via the script tag. See here - https://developer.apple.com/documentation/mapkitjs/loading_the_latest_or_a_specific_version_of_mapkit_js how to include the map.