There is a weird moment toward the end of the 1990s when Microsoft is trying to show their NT is a serious competitor in this space.

Traditionally this was a profitable niche, Microsoft would like to take a fat piece of that, and instead what happened is that Linux destroyed the profit margin. A million dollars overhead that would have kept a hungry UNIX® vendor alive on your project didn't turn into an extra million dollars on Microsoft's balance sheet, instead it evaporated because Linux is "free". And so then Microsoft lost interest.