The first two were due to their anti-competitive strategy not working for them. You can only build the moat if you've already got all the customers inside. Microsoft consistently bet on closed systems: Compuserve-like "information superhighway" rather than the Internet, ActiveX versus "DHTML" (which would become Web 2.0) and Flash.

The "bad" OSs weren't really that bad, but they were attempts to force a big change on people without too much choice, and people absolutely hate that. Note how the successors kept most of the same underlying features while dialling back the UI redesign.