Microsoft was trying to get companies to write Windows software in 1986-87. At the time, it argued that developing for Windows was developing for OS/2 PM.
Borland, Ashton-Tate and Lotus refused. In late 1987, Philippe Kahn said "People are afraid Microsoft is going to take control of the operating system." [1]
Microsoft was afraid that IBM going to take control of the operating system.
Windows 3.0 was enough of a success for Microsoft to intensify it efforts....