It wasn't a Utopia. Right from the start man pages reported BUGS, though many were infelicities, not implementation errors. Dennis once ran a demo of a ubiquitous bug: buffer overflow. He fed a 2000-character line on stdin to every program in /bin. Many crashed. Nobody was surprised; and nobody was moved to fix the offenders. The misdesign principle that "no real-life input looks like that" fell into disrepute, but the bad stuff lived on. Some years down the road a paper appeared (in CACM?) that repeated Dennis's exercise. Actually security (or at least securability) was a conscious theme from the start to which Ken, Bob Morris, and Fred Grampp gave serious attention. Networking brought insecurity, especially to Berkeley Unix. But research was not immune; remote execution via uucp caused much angst, but not enough to kill it. In regards to the basic question. To oversimplify: Theme 1. Unix facilities encouraged what Brian recognized and proselytized as software tools. Theme 2. OS portability was new and extraordinarily final. Subsequent OS's were all portable and were all Unix. Doug