This is what I think. It's the old business model, which worked when everything was expensive, only really needed by big corps with deep pockets, and any machine a teen would have at home had nothing in common with the big irons at some insurance company. IBM would make big money, consulting firms would make big money, you being good with AIX would make big money.
Then with Linux, you could have what could run on any big server, for free, as a teen in your bedroom. You could poke at everything, look at the source code, ask around how you do this or that, since knowing how to do X wasn't some well-guarded secret to have an advantage over the competition, but something fun to share. Eventually those teens would get older and look for jobs or go to university, while at the same time Linux keeps on maturing, and now if you as a company want to build some system from the ground up, or just replace something ancient, you can pick that expensive well-established system from IBM, requiring expensive experts to maintain them, and program for them, expensive software, ... or go with that free OS that a lot of people know their way around with and ask for a much lower salary.
Of course, this didn't happen over night, especially the "it's free but there is nobody to yell it if it breaks" aspect of open source was very strange to $BIGCORP and seen as an unacceptable risk, but there was a steady shift towards that, also in large parts because it was pioneered by all those late 90s/early 2000s tech startups that were exactly created by those "Linux teens". Because that's what you tinkered with in college, not some proprietary OS that you couldn't even afford, or get updates for, or ask anyone for help if you got stuck.