if entry has specific category, show specific html block
craft.entries() returns an EntryQuery. You must then execute the query with one of those methods:

one()
all()
count()
exists()

In your case, I think .exists() is the best choice: {% if categoryListings.exists() %}
Edit: You may also have to execute your category query with {% for category in craft.categories().group('catGroup1').all() %}. See https://craftcms.com/docs/3.x/categories.html#querying-categories.