Actually, this isn'true. Kaczynski has been able to explain the Fermi paradox perfectly logically.
"The theory we’ve outlined here provides a plausible explanation for
the so-called Fermi Paradox. It is believed that there should be numerous
planets on which technologically advanced civilizations have evolved, and
which are not so remote from us that we could not by this time have detected
their radio transmissions. The Fermi Paradox consists in the fact that our
astronomers have never yet been able to detect any radio signals that seem
to have originated from an intelligent extraterrestrial source.32
According to Ray Kurzweil, one common explanation of the Fermi
Paradox is “that a civilization may obliterate itself once it reaches radio
capability.” Kurzweil continues: “This explanation might be acceptable if
we were talking about only a few such civilizations, but [if such civilizations
have been numerous], it is not credible to believe that every one of them
destroyed itself.” 33 Kurzweil would be right if the self-destruction of a civilization
were merely a matter of chance. But there is nothing implausible
about the foregoing explanation of the Fermi Paradox if there is a process
common to all technologically advanced civilizations that consistently leads
them to self-destruction. Here we’ve been arguing that there is such a
--Theodore Kaczynski, Anti-Tech Revopution (2016), p. 55.
For more on the process he describes, read chapter 2 of aforementioned book. Of course, most people who believe in scientific and technological progress--including most members of the middle class and professionals--will find this extremely disturbing: the idea that their own efforts in promoting technological growth ARE the existential risk.