(If you want to know more about how Windows 3.0 delivered this, Kalinina links to a deep-dive Inside Windows 3.) It was not Microsoft's machinations that sank OS/2. Microsoft's management didn't know ...

The primary mode for Windows 3.1 and Windows for Workgroups. It used the 386's virtual capabilities, and DOS applications could be multitasked in the background and run in resizable windows.