Most of those companies are moving forward under inertia, while losing bits and pieces of themselves along the way.
IBM hasn't really been relevant for years. They are now mostly a contracting company that has the resources to develop large-scale solutions. It won't be the cheapest, it won't be the best, it won't be the most innovative -- but if you have enough money, they can eventually make something that does what you want.
Microsoft is struggling to stay relevant. Out of their entire portfolio, they really only have Windows, Exchange, and Office. Most of their stamina is just because they cover the complete business infrastructure (Windows Server, Exchange, IIS, SQL Server, etc.), and because everyone needs to read .doc files. Linux + Apache is a better web server, NetWare was a better directory service, Exchange is kind of in a niche that for some reason no one else has been able to capture (although some have tried and failed), SQL Server is somewhere between MySQL and Oracle -- one or both of which could probably take over any given application just as well. If Linux had better PR and some good project managers, Microsoft would drown. Interestingly, Apple had the opportunity to play the long game here, and instead, cashed in their chips.
Intel is constantly just inching past AMD on the desktop market, and is losing ground to ARM in the portable space. Server-wise, they're still doing quite well. They're on a bit of a precipice now.
Apple isn't really so much an innovator as just the right product at the right time. iPods were not the first music players -- but using a hard drive was a smart move. The iPhone wasn't the first PDA + phone, but when the tech got good enough to be consumer-compatible, it was the first one to put the pieces together in the right order. They're surprisingly capable of rising from the dead, but their current success isn't permanent either.