It's not a plothole: if it happened that way, there would be no ME3 or it would take 3 minutes (reapers come, invade, get the Citadel, shut down the relay network, Shep stucks on Earth and dies, reapers wipe out the galaxy in a few decades or centuries... happy ending). I guess this "small" mystery is a better option from a stroy telling POW.

It is evident that Bioware cornered itself with some reaper related stuff in ME1. They made them invincible and gave them tatctics that nullifies everybody else's. They had to change that in some way (kkhhhmmm..khmmm... Crucible...just to pick the most obvious example).
Why the reapers do not shut the relays down? We don't know. It's not explained anywhere and even if it was explained in any way, we (BSN) would call it a retcon or cheap cop out, no matter what. If we wanted it being logical and "realistic" the reapers should destroy us in a whim.
Playing around with ideas pulled out from my ass (my ideas for a possible explanation):
For example maybe the reapers changed plans for this cycle since they were discovered way earlier than in the previous cycles and their original plans were sabotaged. So maybe it's an intentional decision from the reapers part. Maybe for strategic reasons. They start an assault against all the major military powers at the very same time (by reaper standars). They also previously chose humanity as their primary subject of harvest so they don't linger and start the harvest immediately while keeping the rest of the galaxy busy. So they may think that it's easier to devide and conquer this time. God knows why.
Or maybe the reapers use this cycle as another guinea pig and opportunity to study organics and their strategies, social behavious for their evolutionary experiment (since the organics managed to sabotage their original plans this time). They examine what happens when the galactic government and military command (the social strutcture and system of power) is intact. Or they are curious what makes this cycle tick: what are its weaknesses and strengths in order to avoid situations like this (ME1, ME2) in the future (they want to learn in order to adapt). So again intentional. Mind you that the reapers believe that the organics don't know of the Crucible any more (it shows that they are not that all knowing and omnipotent).
Or there could be this technical issue as well. The Citadell is just a part of the Catalyst or Intelligence (the reapers' collective conscious, knowledge and purpose), but its not controlled by it. Maybe part of it's original hardware dwells there too. But according to what we know it's only used as a conductor of dark energy (mass effect): it's a huge relay to dark space, and the heart of the relay system and its also used as a devise to manipulate space faring societies to make a huge step forward in technological and social evolution and of course it is the "womb" for the creation and birth of a new reaper, as we learn it in ME3 . But it is not controlled by the Catalyst, nor the reapers directly. It is controlled via the keepers and the keepers have become independent since the Ilos relay-project. So they can't manipulate it, only by direct interference (see Souvering's plan).
When TIM (after his indoctrination is complete) tells the reapers that the allied forces do have the Crucible, they immediately invade it and take it away. And then it is easier for them to start the creation of the new reaper at once and lure the allied forces to the heart of their armada where they can destroy them all in one battle along with the Crucible. Thanks to Shepard, Anderson and Hackett and the efforts of the allied forces it does not happen.
This is my theory. But it is an interpretation or head canon if you like. I dare to imagine stuff that's not fully or explained at all in stories. Every story has a level of mystery and unexplained details. So I don't get why it is such a shock or why people afraid to come up with their own explanations, interpretations. Nowadays it has to be all there... in detail, and it also should be logical (?) and very, very realistic (???). Maybe I'm a bit too old school... and less techy-detail-geeky-anal kind of person.
Modifié par GimmeDaGun, 21 janvier 2013 - 08:12 .