Sure, you can create an important event with all users as attendees so every employee can find the event in their calendar. If you want to create multiple events in batches, you may need to call the batch API or use automation.
If the user wants to get its calendar events through the app, then just make sure the app has the Calendars.ReadWrite
delegation permission, then log in to the app using the target user to get the delegation token, and then call the GET /me/events API.
Hope this helps.
If the reply is helpful, please click Accept Answer and kindly upvote it. If you have additional questions about this answer, please click Comment.