I recently deleted a contact form plugin (HubSpot All-In-One Marketing) on a site and the contact forms stopped working.
Curiously, the forms work when the plugin is installed and INACTIVE, but they do NOT work when the inactive plugin is DELETED.
This means that the plugin being present is affecting the site even when it is inactive. How is this possible? How can a contact form work when a plugin is present and inactive, but not when the plugin is deleted? Can an inactive plugin load script files?
Note: The full form code snippets are being included in the page (not shortcodes or anything else referring to the plugin).