" fix some annoying if trivial restrictions "
OS/2 had a single input queue that still could lead to all application freezing because a single one didn't process messages. That was already avoided in Windows 95. Windows 3.x application support was good enough (but not for all applications) - but a lot of software quickly moved to 32 bit, well, because 16 bit. Anyway Apple OS was still worse without pre-emptive multithreading at all. Just it had the applications, at least for a specific sector of users.
Moreover OS/2 lacked "newer" development environments that were appearing on Windows like Visual Basic and Delphi (or even PowerBuilder!) - which made writing a lot of custom GUI application quicker and easier to take advantage of the then new Client/Server world- with all the defects of their approaches, maybe, but they made Windows the platform you could easily code for - and Visual Age couldn't really compete.
Maybe Borland (and others) made a mistake not supporting quickly enough a non-Microsoft OS, but probably IBM didn't inspire much trust too - remember when it tried with PS/2 and Microchannel to close the PC market? Yet most companies back then were not large enough to be able to invest on parallel product lines at the same time.
Anyway even after acquiring Lotus IBM kept on investing in Windows applications and not OS/2 ones. It looks IBM didn't trust itself too....
Biting the hand that feeds IT
