Bubble will automatically focus the first input field in a popup. To avoid this, use this plugin. You need to set attribute ID to the first field focused by Bubble when you open popup. Add the Blur/Unfocus element on the page itself, not in popup. Use the ID Attribute into the Unfocus / Blur Input Action after the Show popup action. A delay may help to be sure input field is visible before the action run.
Demo: https://sandboxjc.bubbleapps.io/unfocus
Plugin page: Unfocus / Blur input Plugin | Bubble