Something I found that helps is emailing the calendar to the new owner. Just right click on the calendar, email (make sure it emails as an attachment), then select who it's going to. The new owner will open up the calendar and save it, it will save under "Other Calendars", but they can move it to "Shared" or "Personal". The new owner will have their own version created (thus making them the admin of that calendar) and can share and continue working with it from there. So far we have not had problems with this process. Hope this helps!
EDIT
By the way, I would only do this with one person and let them share it. When you email it, it will not sync with the original copy, only shared calendars do that.
3This does not actually change the owner of the meeting. Rather, it is a convenient solution for the new organizer to easily create a duplicate meeting; though they will still have to manually set the date, time, and recurrence pattern. Basically, instead of leading with "It is possible", you should lead with "It is not possible, but here is a workaround". – Dan Henderson – 2016-08-03T20:10:13.127
Here's an explanation with screens and video: https://www.extendoffice.com/documents/outlook/4401-outlook-change-meeting-organizer-owner.html
– Jowen – 2018-04-05T11:26:25.890