First off welcome to the Pipedream community, happy to have you.
I think I may see the issue. If you read the help text under the Records property in that Airtable Create Multiple Records action, it says
Provide an array of objects. Each object should represent a new record with that column name as the key and the data to insert the corresponding value.
This means that while {{ steps.trigger.event.title }} may be a valid string, the action is expecting an array of objects.
For example, if you want to insert a title entry, it could look like the below: