When a chat room owner is deactivated, the next user who has been in the room the longest automatically becomes the new owner.
For example, a chat room contains 3 users, User A, User B and User C. User A is the owner with User B joining a day after its creation, and User C joining a week later.
If User A is deactivated, User B will become the new owner and a system message will be posted to notify all other users, User C, that the owner has changed.
Note: If the deactivated chat room owner is reactivated, they will not automatically returned to being the chat room owner.
Note: This functionality is by design and there is no setting to amend this.