I started early 90s and it was a much smaller world. Systems were less complex so there was less to know. Books and manuals were also better so you could read a few books and have a decent understanding from the ground up.

I also believe that until sometime in the 90s most programmers genuinely were interested in computers and didn't just do it to have a good job. So you didn't have to deal with a lot of zealots or clueless people like there are around today.