@ckmoocow , another role of Merge node is to prepare the combination of data you need for your final Trello call. You have not configured Merge1 node for that task. Once you done it right, you do not need to use data from nodes engaged prior to Merge1.
I’m guessing here as I have never worked with Calendar and Trello nodes and, hence, not sure what their output looks like. However, I think the below example can help you to finish building this workflow successfully.
I use Multiplex mode in Merge assuming you have 1 checklist ID from Trello and a few Calendar items to be added to the checklist. Multiplex provides a combination of items where each Calendar item is combined with the checklist ID. As a result, your checklist will be populated with the Calendar items.