Because Quantum! It’s science! Well - one scientific essay... :)
and it’s just as good as any explanation....

I propose that much recent history can be explained by hypothesizing that sometime during the last quarter of 2016, the history of the world underwent a macroscopic quantum tunneling event, creating, according to the Many Worlds Interpretation, a new branch of the multiverse in which my consciousness and that of my readers is now trapped. [...]

We know that quantum tunneling can change the low energy laws of physics in the different branches of the wave function. Alternative facts may simply be the reflection of the media’s ignorance of the state of the world after a quantum transition of this magnitude.

Given the extensive amount of - evidence in the actual paper as well as some subtle hints, I - am not perfectly convinced the author is 100% serious about his hypothesis, though... :)

3 The Evidence
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Acknowledgments

The work of T.Banks is NOT supported by the Department of Energy, since that Department, and all other Departments of the Federal Government not directly concerned with Security or Making American Great will soon be eliminated.