Pruning *episode 4 spoilers*

The post credits scene shows that pruning someone doesn't erase them, because Loki wakes up after his pruning, in a world that presumably contains all the other pruned Loki variants.

The TVA obviously has some immense power source to not only exist outside space and time, but also time travel as well as negate magic.

My theory is that they harvest energy like the weeping angels from Dr Who. When they prune a variant they chuck them in some temporal holding pen outside their proper timeline and steal their potential energy.

The chaos that surrounds Lokis probably provides a whole heap of energy, so they keep pruning Loki variants to use them as a big battery.

This ties in with other theories that the sacred timeline is just a specific timeline that someone (Kang) want to exist for some reason. If the TVA just wanted the timeline gone they could just place the bomb and wipe it away without involving the variant that caused the branch at all instead of kidnapping them from their timeline before wiping it.