The first Apocalypse was caused by Rushy and Tim both. During his mission to save Tim, Rushy dialed Destiny from Destiny, hoping to use the Teal'c effect. Instead, he ended up dialing a past version of the ship(due to time being fractured). At the same time as Rushy time-traveled, Tim closed the fractures.
As a result, the wormhole connection became incredibly unstable and began sending a Rushy from every millisecond in time through every Stargate, finally collapsing time.