Exar Kun sends Ulic Qel-Droma to do to this Mandalore exactly what he did to the last one? not sure but it sounds plausible.
Or Exar Kun goes himself and challenges Mandalore, game over.
Why would you wipe out an opponents' powerbase when you can win it through an easy duel.
Mandalore would be foolish to accept a duel. That way Kun has to get to him first...