"in 1998, what else would you have used?"
RS/400, OS/390, VMS, TOPS-10/20, Netware, RISC OS, need I go on?
"Linux was in its infancy (as in crawling, falling over all the time and spreading shit everywhere)."
Horse shit. I had been running Slackware exclusively as my primary desktop for about 5 years in 1998 ... and in 1998, I was rolling out custom Slack installs at businesses & schools all over the SF Bay Area (mostly servers, granted, but then that's what we are talking about here).
"Various *nix versions were stable but all needed a whole lot of specialist knowledge to write stuff for"
Well, DUH! NEXTSTEP, AIX, HPUX, DigitalUNIX, SCOunix, Xenix, SunOS/Solaris, the BSDs, et alia, aren't toy OSes, designed for home use ... They are professional tools. That's why us professionals used them.