Sharepoint - SharePoint Events Not Showing In Calendar, But Will Show in All Events List (SharePoint 2010)
See if the below threads help in your situation. I've copied excerpt from the 1st link below.
It sounds like you have switched on the "Group Calendar Options" for your calendar. These add new content types to the calendar ("Schedule", "Reservations", and "Schedule and Reservations") in addtion to the standard "Event" content type. These new content types each come with their own specific behaviour. Yor screen shot showing the Attendees field looks like it's using the "Schedule and Reservations" content type.
To check this, go to the "Title, description and navigation" settings page for the calendar (this is the first option under "General Settings" on the List Settings page). You will see two settings in the "Group Calendar Settings" sections. Set both of these settings to NO. This will remove the special content types from the calendar - you will be left with only the standard "Event" content type, which should then behave like you are expecting (ie, everyone can see all events).
See also: https://social.technet.microsoft.com/Forums/sharepoint/en-US/8a18f211-ecff-44c8-93d9-53d1eb36dece/enabling-resource-reservation-causes-calendar-events-to-disappear?forum=sharepointadminprevious