A team in Microsoft Teams or a Microsoft 365 group can become ownerless if an owner's account is deleted or disabled in Microsoft 365. Groups and teams require an owner to add or remove members and change group settings.
You can create a policy what automatically asks the most active members or an ownerless group or team if they'll accept ownership. When a member accepts the invitation to become an owner, the action is logged in the compliance center audit log. Guests are never invited to be owners.