This let _some_ clean Win32 apps run on 16-bit Windows 3.1. As a demo it bundled the original Freecell game. It's still out there as a free download today, and gets you the original tiny fast Freecell on Win11 64-bit, including on Arm.
IBM had licenses to include full integrated copies of DOS and Windows 3.x with and inside OS/2, called "WinOS2". But it was 16-bit Windows and ran on the OS/2 DOS VM.
Win32s let some apps run, but Win32s didn't work on WinOS2. IBM tweaked WinOS2 to get Win32s working. MS responded by tweaking Win32s so it didn't work.
Repeat multiple times until MS hit a way to stop it working at all.
So, apart from a few trivial apps that ran on older versions of Win32s, you could not run any Win32 apps on OS/2.
So, Microsoft moved the market to 32-bit as fast as it could, first with NT 3.1, then NT 3.5 which introduced the VFAT disk format and long file names, then with the consumer-focussed Win95, then with NT 3.51.
So all the cool new apps ran on Win32 and OS/2 was frozen out of the market.
Ah, then you are missing a critical detail.
OS/2 >= 2 could only run 16-bit Windows apps. No 32-bit.
So very much not "all", no no, not at all no.
Right after OS/2 2.0 shipped that got very important very fast.
Windows 3.0: 1990.
OS/2 2.0: early 1992.
Windows 3.1: late 1992.
Windows NT (first release, first 32-bit version of Windows): 1993.
Windows 95: 1995.
There was a "shim" for Windows 3.1 called Win32s:
https://en.wikipedia.org/wiki/Win32s
This let _some_ clean Win32 apps run on 16-bit Windows 3.1. As a demo it bundled the original Freecell game. It's still out there as a free download today, and gets you the original tiny fast Freecell on Win11 64-bit, including on Arm.
IBM had licenses to include full integrated copies of DOS and Windows 3.x with and inside OS/2, called "WinOS2". But it was 16-bit Windows and ran on the OS/2 DOS VM.
Win32s let some apps run, but Win32s didn't work on WinOS2. IBM tweaked WinOS2 to get Win32s working. MS responded by tweaking Win32s so it didn't work.
Repeat multiple times until MS hit a way to stop it working at all.
So, apart from a few trivial apps that ran on older versions of Win32s, you could not run any Win32 apps on OS/2.
So, Microsoft moved the market to 32-bit as fast as it could, first with NT 3.1, then NT 3.5 which introduced the VFAT disk format and long file names, then with the consumer-focussed Win95, then with NT 3.51.
So all the cool new apps ran on Win32 and OS/2 was frozen out of the market.