Most of 1980s companies didn't survive, whether they competed with Microsoft or not. Microsoft did, but that doesn't mean it killed every other company that didn't.
But Microsoft competed with Apple, and Apple didn't die. Xenix - Microsoft's UNIX offering - went nowhere (though it wasn't even MS product, technically), and other Unixes still alive. In DOS times, there were pretty successful competitors to MS-DOS (of course, those died when DOS computing died, but I'm not sure this qualifies as direct competition).
Most of 1980s companies didn't survive, whether they competed with Microsoft or not. Microsoft did, but that doesn't mean it killed every other company that didn't.
But Microsoft competed with Apple, and Apple didn't die. Xenix - Microsoft's UNIX offering - went nowhere (though it wasn't even MS product, technically), and other Unixes still alive. In DOS times, there were pretty successful competitors to MS-DOS (of course, those died when DOS computing died, but I'm not sure this qualifies as direct competition).