I had Windows 1.0, which was pretty useless. Windows 2.0 was only a tiny bit better. But when they introduced Windows 386 (based on 2.1, IIRC) it became pretty useful. It had a protected mode kernel, and I could run multiple DOS apps in separate windows. It started selling pretty well, and a ex-Microsoft guy told me it really got their attention, and they realized they might not need IBM after all. They put a huge effort into Windows 3.0 and began to lose their drive for OS/2. IBM was making it hard for MS because they knew MS wanted to sell OS/2 to everyone and IBM wanted some features for themselves to help push IBM hardware.
Using Windows 386 as a DOS task switching platform created the opening for Windows apps. Being able to run Ami Pro (word processor), Micrografx (drawing) and later Excel was a bit of a game changer. Before, I waited months for drivers to appear for a graphics board I got for AutoCAD, and had to run 640x480 for Word Perfect, Lotus 123, etc. After about 6 months, I could run all three at 1024x768. Then I got a NEC Laser printer and waited months for drivers. That was pretty painful. With Windows 3.0, once I had drivers, all the apps worked. That sold me. When Pagemaker arrived, it worked perfectly with my graphics card and drivers. All I needed for hardware upgrades was Windows drivers and AutoCAD (DOS) drivers. Life got so much simpler. I read Gordon Letwin's book "Inside OS/2" and figured when the DB-based file system arrived, it would win and easily beat Windows. That file system never arrived and there was never a reason to leave Windows. But MS seems to trying to give us lots of reasons today.