For Flow + collectionCreate: ruleSet must sit inside input, and relation should be EQUALS (not “IS EQUAL TO”). That gets you proper smart collections; publishing is a separate publishablePublish step.
If you’re creating hundreds from tags/vendors and don’t need Flow, I built Collectify – Auto Collections to bulk-create those smart collections from existing catalog attributes (disclosure: I’m the developer). Free for 10, then $5 one-time. Search “Collectify” in the App Store.