They find out about things like Discordian philosophy, Douglas Adams, Monty Python. Suddenly they have something in common with the other weirdos. Finally, you've got cohorts worth having and a collective mission to find the things worth paying attention to. Back to the sysadmin thing. At some point, the geek discovers computers.
Computers are complicated and daunting to most people.
To the geek, a computer is a challenge and a toy. Given a problem to solve or an intriguing thread to follow from moment to moment, that sort of geek will focus so sharply that they forget to eat when hungry. They find they're good at dealing with computers. Some of them find that they prefer to write code, building new entities a line at a time, tinkering and reworking them, never quite satisfied. They're sort of the architects of computing.