Why did the tunnel not collapse properly in Cabin in the Woods?

Question

Curt, Dana, and Holden are trying to flee the cabin on the Rambler by going back through the tunnel; it's supposed to have been collapsed by now but Demolitions had a little glitch and the tunnel was still open. Fast-forward to when everyone is celebrating because they think the ritual is over. Sitterson comes over to Demolitions and is talking to them about what happened and they say

DEMO #2 : No, seriously. That wasn't on us. There was an unauthorized power re-route from upstairs.

Sitterson stops mid-drink, frowns. Wait —

SITTERSON : What do you mean, "upstairs"?

Sitterson becomes very serious and concerned but the red phone rings and we don't get anymore info from Demolitions.

So, who is "upstairs"? And why would they (seemingly) want to let the kids escape if they know that this would lead to the DESTRUCTION OF THE WORLD!?

Answer 1

The glitch was caused by the Fool. At 47:00 he discovers the wiring in the house and notes that it leads into the corner of the room. At 48:50, he's dragged into the forest and, after having dispatched Judah Buckner he discovers the elevator entrance.

The next time we see him (1:05:50), he's literally elbow deep in the electrical system, trying to power the lift. Obviously that power has to come from somewhere...

The original script makes it a little clearer what he's been up to:

MARTY (CONT'D) : It's an elevator. Somebody sent these dead fucks up to get us. There's no controls inside but there's maintenance overrides in there. I been playing around. I think I can make it go down.

As regards the "upstairs" line, this Reddit AMA with Director Drew Goddard shows that he clearly considers 'downstairs' to be the machine levels and 'upstairs' to be the cabin level:

By the way -- the game was gonna be amazing. You were gonna be able to play in both the upstairs "Cabin in the Woods" world and the downstairs "facility" world with all the monsters. Believe me, I HATE all video games based on movies, they always suck, but porting Cabin into Left For Dead felt like the right fit. It pains me that it didn't happen.

Answer 2

My interpretation of the scene was that there was no actual power re-routing from "Upstairs". Rather, the glitch was the result of the Shaggy analogue having screwed with the wiring, which diverted power, and Demolitions either thought that Upstairs did the rerouting of power and just didn't tell them or they were looking to cover their ass.