Windows 3.x was the first viable version...
In particular - I bet if we made this a little more granular, most respondents are talking about Windows for Workgroups 3.11
A few things happened...
640x480 VGA and then 1MB SVGA cards capable of 800x600 and 1024x768 resolutions.
OLE and dynamic device driver consolidation really came of age...
The Intel 386DX 32 Bit processor - and maybe more importantly, the AMD 368 processors that were just ever so much faster (386DX40 vs. 33).
And relatively easy network connectivity between workstations.
Most people were buying Win 3.x - too, not getting it bundled. It was not yet a default on PCs - many of which still came only with DOS 5, 6 or 7.
At least, that is my recollection. People forget that shortly before Windows 3 - DOS Shell was still big, and Duke Nukem was a non-3D EGA side-scroller, and lots of people still went with Hercules Mono graphic cards in your choice of amber, green or VGA paper-white to save money (well, not the adapters, but the CRTs that plugged into 'em).