Someone maybe has generated the same private keys as you? It's extremely unlikely, but not impossible!
When people jump first to "duplicate private key" it makes me wonder if they jump to the least probable explanation in other scenarios as well.
Say you came home from work early, open the door to your house, and saw your wife having sex with the neighbor.
Now there are two (well probably more but let keep it simple) possibilities:
a) Your wife really is cheating on you, with your neighbor. The proof is irrefutable and visibly obvious in front of you.
OR
b) On your way home from work, unbeknownst to you, you were transported into a parallel dimension. This dimension for the most part is undetectably similar to "your" dimension, except in this world, you never married your wife. Due to that fact she actually married the man whom you know as your neighbor. So in reality the man and women who are having sex, are married, don't even know you, and this is their home. If they haven't seen you yet you should probably leave before you are arrested for breaking and entering.
I have to wonder when faced with that scenario, if the first words from the "duplicate private key" people would be "
Hey are you my wife? I just need to rule out the possibility that I accidentally traveled between dimensions before I get really pissed."
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