Idea on Kett, jardaan and the Scourge

So yeah, something did happen to the golden worlds to trigger building the remnant vaults and stuff. Then the Scourge hits, screws things up for a century and a half. Just as things get better, the kett come and screw everything up again.

And then we arrive.

Idk. Could be comparable levels of tech but just on different ends of the spectrum. Its noted in game though that teraforming an entire cluster all at once as quickly as the vaults do requires an astounding level of technology. Perhaps the reapers could match this, but they also are capable of being defeated by inferior versions of the same technology they fostered, being that they themselves just use better versions of citadel tech on their onslaught and nothing beyond the understanding of the races they're reaping. Instead of dwarfing their victim's tech with their own they used the citadel previously to amush them in effort to crush rebellion quickly... If they could completely manipulate life/planets on the Jardaan's level (as the Archon wants to do) I think they WOULD.

Maybe the Jardaan forsaw their own inevitable defeat and were trying to preserve themselves after the fact? By placing Vaults to undo damage done after they left?

Voeld's entry states the ice age is a direct result of the scourge, and the scourge didnt spread until it hit the meridian, spreading almost instantly across the cluster from that point on.

But that still leaves about a 500 year gap.