Unfortunately, the “Find Records” action (and the subsequent “Update Record” action) doesn’t work in the way that any of us would expect it to work.
What you were expecting is what most of us were expecting, which is that Airtable would loop through the found Record ID’s and update each one of the records that it found. But unfortunately, it won’t do that.
In your final screenshot above, you’ve pasted in the “List of Record ID’s” into the “Record ID” field, but the “Record ID” field can only handle a single Record ID. You pasted in an entire array of Record ID’s expecting Airtable to loop through each one of those records and update each one of those records, but unfortunately, Airtable can only handle ONE Record ID there.
I would also email Airtable at email@example.com to ask them to improve/fix how this functions.