the fermi paradox asks, if aliens are supposedly so statistically prevalent, why we haven't received any radio signals from them.
here is my independently-developed (though probly not original) answer:
statistically, it seems reasonable that civilizations would accidentally invent unaligned superintelligence not long after inventing radio signals (in our case, a couple centuries). in order to percieve those signals, you would need to exist after your planet receives those signals, but before your planet receives that unaligned superintelligence's expanding sphere of death, which might very well travel at celerity or near-celerity.
thus, given the low probability, it is not surprising that we haven't percieved those; for any given alien civilization, in a given timeline, we either haven't received their radio signals, or have already been killed by them. seeing as we're alive, this timeline must be one of the former.