At that point(1989), the future was less clear-cut than Windows vs OS2. Windows was more a graphical shell for DOS than a real OS, and there were other graphical shells for DOS. From the top of my head: I vaguely remember GEM, I have used one from Tandy. There was something else installed on our school computers, Dynamic Environment or something . Windows before 3.0 (1990) was inferior to a lot of these DOS shells.
If the choice was between 2 options, 'both' might be a viable response. But 3 or more, especially with a market expectancy that everything DOS-based would disappear?
You may be thinking of DesqView? It provided some level of virtualisation and multi-tasking, if you had a competent-enough CPU. Eventually, there was also DesqView/X which allowed you to export DOS and DesqView-aware applications over X11, which was actually kind of cool.
Right, and Microsoft was still putting so much development work into OS/2 in 1989 that there was still some sort of feeling that OS/2 was possibly the future of Windows. (OS/2 development kits were shipped from Microsoft with Microsoft branding prominently on them right up until the OS/2 3.0 [WARP] split and the origins of Windows NT.)
In hindsight it is much more obvious that Microsoft's involvement in OS/2 was something of a trojan horse to fund early NT development and a short-term hedge in case people did trust the IBM brand more than the Microsoft brand, but at the time it was much more confusing.
If the choice was between 2 options, 'both' might be a viable response. But 3 or more, especially with a market expectancy that everything DOS-based would disappear?