Scientifically, this means that:

ANITA saw radio signals that it could not explain,
their leading hypothesis was that high-energy tau neutrinos are traveling upwards through the Earth,
and that hypothesis was refuted by IceCube observations,
teaching us there is no astrophysical point source out there that is creating the particles that ANITA is indirectly seeing.

So where, in all of this, do the parallel Universes come in?

Because there were only three explanations for what ANITA saw: either there was an astrophysical source for these particles, there’s a flaw in their detector or their interpretation of the detector data, or something very exotic, remarkable, and beyond the Standard Model (known as CPT violation) is happening. Some very good science ruled out the first option (back in January), which means it’s almost certainly the second option. The third? Well, if our Universe cannot violate CPT, maybe this comes from a parallel Universe where CPT is reversed: an explanation that’s as unlikely as it is poorly reasoned.