In hindsight it is much more obvious that Microsoft's involvement in OS/2 was something of a trojan horse to fund early NT development and a short-term hedge in case people did trust the IBM brand more than the Microsoft brand, but at the time it was much more confusing.

Lotus was bigger than Microsoft for most (all?) of the 1980s.

Wordstar was another company that failed to understand the shift to GUIs.

Of course, Wordstar had another major marketing problem. Despite its dominance, nobody knew the name of the company (MicroPro) that made it. Far too late they realized the mistake and changed the company name to Wordstar. Microsoft never made that mistake.