Tightly related to other questions:
- Did ~spoiler event~ occur in the original, looped Agents timeline?
- When was ~character~ supposed to die in the looped timeline
This whole question is going to be spoiler heavy up to the end of season 5.
What we can observe
So, shockingly, they managed to break the time loop. I know... who would have predicted that!
We know that in both loops Daisy leaves the Quinjet, and shouts something at another occupant before she walks away (we infer the Coulson was inside it in both timelines.)
We assume that in the looped timeline, Talbot and Daisy fight, Talbot overpowers Daisy and Talbot absorbs her, and then shatters the Earth.
The change point is implied to have been Coulson's decision to not take the serum, but that doesn't start to change Daisy or Talbot's behaviour until the point at which she notices the serum in her glove.
What was Coulson doing in the original timeline?
If he took the serum, why didn't he join Daisy trying to talk Talbot down?