Ok if the catalyst was in the citadel all along and was in fact responsible for the cycles of extinction, why the heck would the reapers need the keepers to activate the citadel's relay which lets them enter the galaxy from dark space? Why bother even having the whole concept of the keepers at all if the catalyst can controll or operate the citadel? Also, if the catalyst is this all powerful entity, couldn't it have simply restored the signal when the prothians from illos disabled it centuries ago? this makes no sense at all and just proves the fact that there was a breakdown in the writing or that the developers just stoped caring. But if anyone has any thoughts on this matter please let me know.