Zarek sneakily observed his surroundings, and when he saw that the people had yet to start focusing their attention on him, he planned his escape route.
If he stayed any longer, it was only a matter of time before the people recognized him and points him out. It is something that should have been done sooner considering he was never a good lord to the people.
Embezzlement, abuse of power, corruption. Name all the negativity present in a lord, that is what Zarek's image stands for.
The only reason why they had yet to rat him out, was because Avidius their emperor had committed an even greater sin, going against the will of the chapel of the nine Gods.
But now? None of those matters anymore because their lives are in danger if they do not do as the monsters said. They owe him no obligation to keep his life from harm at the expense of theirs.