Intuitively you will use mouse wheel to zoom in, zoom out the map.
That is default by almost all map on market.
Only exception is if google map embed in a web page, that page is too long, page becomes scrollable.
When you use mouse wheel, it only scroll the page, not zoom in or out the map.
Google has the idea to detect whether the web page 's vertical scroll bar is present, if it does, then popup a hint to suggest you to hold control key while turn mouse wheel will zoom in or out.
I hope ESRI will do the same in the future.
Currently ESRI did not fix this problem, when you turn mouse wheel, it only scroll down up the page, not zoom in out,
See this post,
Mouse Wheel Zoom
https://community.esri.com/t5/arcgis-storymaps-questions/mouse-wheel-zoom/td-p/1012133
ESRI provide a temp work around is to use 'Embed' option to embed story map into parent page, but it does not good as how google map fix this kind of problem, use ctrl+ mouse wheel
For current Los Angeles county map user, your only option for now is use + - button at the right bottom corner to zoom in out.
https://storymaps.arcgis.com/stories/400d7b75f18747c4ae1ad22d662781a3
