I think time has possibly been stopped- rewound- things changed and whatever they wanted. Familiar faces in the past. Old buildings that can't be duplicated. Maybe different locations are older than others or locations reset differently than others. I don't think it could be planned out by so many people without redos and rewinds.
If that was possible and the case, then they'd already have completed their goals. Time Travel to the past can only make some logical sense, if a new timeline/ branch is created at the point you travel back to, but in the timeline you left, you simply disappear and nothing changes there. Time Travel to the future would be a lot like putting yourself in stasis whilst everything else fast-forwards. But I have only ever considered Time Travel to be a fiction.
Interdimensional beings, however, they are more believable.
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