The Unabomber case was more complex to track [1]. I'm not suggesting it was because he had a higher IQ, as someone with an average IQ could have executed similar actions successfully.
It was also in a time where not everything got recorded. You have to think that having cameras everywhere and much more complex package tracking systems like we do now would have made staying hidden quite a bit harder.
[1] https://en.wikipedia.org/wiki/Ted_Kaczynski