At the time Windows 95/98/Me lacked certain features so it's possible they wanted to experiment with things like multi-threading/processing. NT also supported Intel's physical address extensions, PAE, to address 64GB of RAM using an extra 4 bits of memory address creating 16x 4GB banks. Might have helped them in the development phase as map compiling took a lot of resources back then. Its also possible they saw that NT was the future of Windows as Win 2k married the multimedia stack of Win 9x with the more capable NT kernel. That led to XP which finally killed the Win 9x family.
I tried running Quake 2 on Windows NT 4 before 2k came out so like '98/'99 but had an issue as NT lacked DirectX. My memory has faded and I don't remember if the installer failed or it failed to run. I think it was the former as I have a recollection of something complaining about missing DirectX.
I do know that multi-processing was implemented in Quake 3 and I specifically ran Windows 2000 for that.
A lot of younger people have no idea how great Windows 2000 was. Before that you could run 9x and have it bluescreen all the time, or NT4 and not have drivers for any consumer level products and the really shitty UI from windows 3x. 2000 was the best under the hood and had the great GUI, and had drivers for most things you'd want to install and was stable and handled networking well. Just all around the best OS at the time.
I tried running Quake 2 on Windows NT 4 before 2k came out so like '98/'99 but had an issue as NT lacked DirectX. My memory has faded and I don't remember if the installer failed or it failed to run. I think it was the former as I have a recollection of something complaining about missing DirectX.
I do know that multi-processing was implemented in Quake 3 and I specifically ran Windows 2000 for that.