Given the fact that he's A Pirate 400 Years Too Late, and that in Ending 6, which is considered the canon ending, the viewer learns that the box is an anomalous object in the space-time continuum that caused it to split in to multiple branching paths and instantly causing a Zombie Apocalypse, it's possible that Magnum was brought to the future the moment the box was stolen.
There's a lot about the box that raises suspicion, mainly the red, green and blue afterimages that flash after it's removed from the podium, the fact that in Ending 6 it's revealed that the box is an anomalous object in the space-time continuum that caused it to split in to multiple branching paths and instantly causing a Zombie Apocalypse, Darkiplier's appearance and his apparent knowledge of what's really inside the box, and Ending 16, in which activating the box takes you directly to Wilford Warfstache.
- The box that caused the whole anomaly is shown to have a blue crystal in the lid. This same crystal would appear as the Warp Crystal in In Space with Markiplier, possibly hinting at a connection.
- It would certainly explain why picking it up caused reality to fracture, although it being disconnected from the Warp Core would mean that the scope of its powers is far more limited, which is why it doesn't cause the destruction of the universe as whole - and why destroying the artifact it's contained in returns reality to normal.
- It could also be likely that the box itself is a specialized container1 for the crystal - which is why the contents vary so widely, with some timelines giving the crystal more influence than others, such as the one where the box contained a time travel device.
