There seems to be no way to transfer ownership of a team from a sole owner who has had their credentials revoked. Changing ownership in the Admin App seems to only affect the 365 group, and has no effect on the team in the Teams App.
Anikke Bukowski commented
This is an important feature for handover of teams when users leave or change roles.
i changed the owner in the O365 portal, but the change has not reflecting in Teams.