I don't disagree with Seika's initial decision to abandon the town, this stampede literally happened because of the actions of the adventurers who live there(because they don't understand the lords of the dungeon are basically stop valves to prevent this very thing from happening), and Seika offering up the information on what caused the stampede and what needs to be done to prevent future ones will put him directly at odds with the Adventurers and potentially the guild itself(not to mention how could he explain how he came to learn this without exposing himself further). This stampede was inevitable, Seika saving the town and potentially exposing his strength(AGAIN) just points yet another target on his back, the same type of target that got him marked for elimination and ultimately led to his demise in his first life. Whether you want to admit it or not, the town is doomed because Seika isn't going to be there to pull their asses out of the fire next time a stampede of this scale happens unless he finds some way to manipulate the dungeon so stampedes literally cannot occur at all.
That being said, I understand why he caved and decided to stay and fight with Amiyu and the rest instead of forcibly extracting her and the rest of the girls out of the city because that decision would absolutely destroy the girls and it would ultimately lead to losing his humanity because he'd have definitively drawn a line in the sand saying "Sure I CAN do something here, but I don't care about them so why should I" which is a very slippery slope because forming genuine connections will be harder because in the back of your mind every positive connection is someone else you're "obligated" to help since that is the value system you've adopted as your own. He would ultimately just be drawn closer and closer to being an actual Demon Lord, completely detached from the majority of people and while not relishing the pain and suffering of those he doesn't care about, would observe happenings like this stampede as if they were just another event and that would ultimately leave him alone because that way of thinking would be completely detached from anyone he'd care to have a meaningful relationship with.
