When the humans and the Cylons made peace on earth, the human discarded all technology but the Cylons knew what would happen before would happen again. This set in motion a chain of events that led them to be targeted for Termination
Spin of Where Angels Fear to Tread. Skynet's escape into an alternate timeline caused ripples to appear in the time stream. This causes more alternate realities to be formed in wake of the War Against the Machines.
The Cycle changes, expands, and contracts anew. It seemed to be finally broken until one sudden change and the cycle is renewed. A threat from the future brings a threat to all worlds and no one knows if it will end for good this time.