Was it possible? Sure. Was the deck stacked so heavily that it makes one thousand percent more sense to skip to the end? I'm also pretty darn sure. (even more so, if even stopping Oban wouldn't change the outcome)
Heck, from an encounter design perspective, put Oban and the sarcophagus far enough into the room to start that the MN can almost get there in time (or so far back towards the entrance that it's clear who let them in, but without time to stop them) throw in some obstacles like lava and/or a cultist or a low level demon or four* to thwart dimension door/step of the wind - - all the drama of "we almost stopped this" without smacking your players hands away from the cookies so much.
BUT that's just like my opinion, as i said the ends totes justified how we got there, for me - but I did require an extra biscuit during my mid-show snack.
*bonus carnage when all those foolish cultists/demons are blown to bits by the summoned.