Whether or not you spell Microsoft with dollar sign it doesn't make every other company the hero.
History has turned OS/2 into some kind of folk hero rather than the bloated, mismanaged, expensive, buggy mess that it actually was. And Microsoft's technology was superior if the job of an OS was to actually run software on computers of the time.
I have read a lot about that time and it doesn't seem particularly biased. Microsoft hated working with IBM and their horrifically old-school way doing software development (e.g. counting lines of code, etc).
The bias, in my opinion, is the other way -- which is exactly what I said at the top.
Letwin says what killed OS/2 was that it could run Windows apps.
This is not true.
That only applied to OS/2 2; OS/2 1 could not run Windows apps.
It didn't matter; there weren't any.
Windows apps followed Windows 3.0. Windows 3.0 followed the failure of OS/2 1.x.
This is his bias: he was one of the project leads and was passionate about OS/2, which blinds him to the fact that it was OS/2 1.x that flopped and there was nothing OS/2 2.x could do to usefully come back from that.
His assertion is that 32-bit OS/2 flopped, because it lacked native apps, because it could run Windows apps. This is not true.
It flopped because Windows 3 was out, and Windows 3 was a hit because it did what 16-bit OS/2 failed to do: it ran DOS apps _well_ and it could do that because it took advantage of the 386 chip.
His bias means he fails to identify the true cause although he named it.
Secondarily, I think we can point to a 2nd, non-technical, personal reason: Letwin was not involved in Windows 3, which was essentially a 1-man skunkworks project.
History has turned OS/2 into some kind of folk hero rather than the bloated, mismanaged, expensive, buggy mess that it actually was. And Microsoft's technology was superior if the job of an OS was to actually run software on computers of the time.