They simple Underestimated the MC.
They know the MC has all the cards that is why they agreed to all his demands... as soon as the MC lets go of the cards... then they assumed that they can just beat up the MC or whoever is behind him.
No coercion? No threats? No torture? No tracker? No spell to distinguish lie from truth? So much for "Kings" of a "higher race". The story makes them too dumb to even think themselves or doubt the MC, just like Yisha.