Well all that happened is they realized that with multiple timelines , they cannot change the future they come from, and since keira 2 and alex 2 jumped into this timeline it became contaminated.
But here is one issue I have , keira 1 was in this timeline , so is this the orignal timeline we started watching, or is it a # 3.
So right now changing the future is sort of pointless, but you can guide things so the future of this timeline does not turn out badly, which is sort of hard to do .
this could be some sort of reboot to the series.