ToEE - the deserted farmstead SPOILERS

[e4mafia]

So.....if the cultist thinks they're being overrun, he makes for the storeroom, and sets off the bombs, leaving a sizable crater in the ground, and absolutely certain death for every person within 300 feet of the cottage (effectively 30d6 damage - 15 force, 15 fire). As characters are expected to be somewhere from eve 2-4 at this point there's just no way they will survive.

I mean playing it straight, if the cultists see the inevitable, its really just down to luck if they make a break for it and survive getting past the PCs. And if they do, everyone's going to die. Just seems like a very clumsy TPK written into the adventure. Of course I can modify, play it differently, and do whatever's right for the table. I'm just wondering why the heck it's written this way in the first place.