Okay, this hostility is unwarranted.
Use your brains goddamnit instead spouting bull****.
The Reapers were afraid of a singularity in case of which an AI develops that is vastly superior to organics.
And then it's decides that they are a threat to its continued existence and attempts to wipe them out.
As a machine intellect it is devoid of emotions and does it's job throughly - eliminating all organic life - including some primordial soup on a planet at a butt end of the galaxy - lest it might someday evolve into something threatening.
And all the time it continues to improve itself, essentially wiping the galaxy bare of resources(which is something that Geth actually begun to do in their space) - thus giving no chance to for organic life to evolve EVER again.
And in the end we have a sterile, barren galaxy with a gigantic supercomputer made out off all the resources. Once the AI figures that it is STILL not enough and there is still room for improvement it will spill over to other, neighboring galaxies to harvest more resources and "build additional pylons"
Now what the reapers do is to purge the galaxy of all advanced organics that are at risk of unleashing such a fatal singularity - and preserving and memorializing it's collective consciousnes in the form of a reaper. All the while all the while sparing younger races.
Yeah - they end existances of trillions of beings each cycle, but it's just a statistic in the grand scale of things - in the end what they do is making sure that organic life keeps existing.
It is all in the probability - with the size of the galaxy, the multitude of races inhabiting at any given time a fatal singularity WILL HAPPEN sooner or later.
And once it happens it's "game over man, game over!" - the scenario that they fear and i described only needs to happen once and it is all over - BAM! no more organics - ever.
Who knows? perhaps the original race begun the cycle after suffering a very harrowing, very, very, very close call themselves in the prehistoric past.
And with the info we have, close calls are actually pretty frequent.
The failed AI uprising in the prothean era taht was dealt with by blowing the ****ING SUN in the respective system and the recent Morning War.
Before any of you jumps out and say "hey! but the Geth aren't hostile, just isolationist!" let me remind you.
Their current plan is to build a massive dyson sphere encasing a goddamn star so they can happily make consensus as one, even better, even faster - what if they decide that it is still not enough?
Sure - our bro, Legion said that they bear no ill will toward the organics and don't care about them one way or the other unless they're try to interfere.
I'll be damned if they don't try to interfere in case of Geth gobbling up a galaxy worth of resources.
In the end what the reapers do, is trying to save us from ourselves - even if we don't want to or won't even acknowlegde or believe taht the problem even exists to begin with.
And more so they realize that their solution is cruel, gruesome and definitely NOT ideal - hence the Guardian if anyone has any better ideas.
Flame me if you wish, but i believe that the singularity motive is a lot better than the Dark Energy bull****.
I hope i have given you a proper context and some food for thought.
Flame me if you wish i don't care