Of course maybe "multiple" really doesn't mean many. Or "possible" really doesn't mean "chance of others." Or "previous" doesn't imply universes existing before ours. I'm sure you can explain.
Indeed, in that I already did, twice.
I am not suggesting there were or are multiple universes. I am suggesting that when a particle could have come from two or more places or states that existed in the just-previous state of the universe, with equal probability, then you have to figure out what the universe looked like in either case, in your omnibus back-calculation. If you make me explain this again, I'm going to withdraw your license to think about what's entailed in attempting to calculate what the world once looked like.