Microsoft was working on Microsoft OS/2 NT 3.0 when they broke off from IBM, and then renamed it Microsoft Windows NT 3.1 using the Windows 3.X GUI. Microsoft also pushed Windows 3.0 and 3.1 that loaded on top of DOS. IBM had OS/2 2.0 that had WIN-OS2 to run 16 bit Windows apps. Then companies quit making OS/2 native apps and made 16 bit Windows apps instead because OS/2 could run them as did Windows.
The big blow to IBM was Microsoft's Windows Tax to OEMs, that is based on how many computers they made, even if Windows was not installed on the new PCs. So if someone wanted to install IBM's OS/2 or Next's Nextstep for Intel chips, or BeOS for Intel, they still had to pay Microsoft the Windows tax. This forced OEMs to preinstall Windows, because they already paid for it with the Windows tax.
So it was a combination of OS/2 running 16 bit Windows programs and companies not wanting to make an OS/2 native version, and Microsoft marketing Windows to be used instead of OS/2 by bundling it with every OEM PC sold, that stabbed IBM in the back over OS/2.
Yes, Microsoft in the 1990s were ruthless and even bundled Internet Explorer with Windows 95 OSR and Windows 98 that got them investigated by the DOJ for antitrust issues.
Microsoft has traditionally been the one to get the hate for this because their moves were so brash in the '90s... But the other big tech companies aren't any better. Apple is a friend of open source and standards only when it happens to suit them. Google does lots of open source but they want to be the ones holding the reins at all tiems (Blink, Android, etc.) Facebook spends a lot of money on looking smart and friendly to developers so that we'd ignore the Orwellian pile of information they hold on most people. Etc.