I think every typewriter/office machine company tried their hand at computers at some point. Royal McBee, Burroughs, Smith Corona (I don't think they did full-blown computers, but they did do some dedicated word processors), Remington Rand...
I think that gives the wrong impression, that office machine companies tried making computers and failed. Remington Rand, for instance, was IBM's principal rival in the 1950's, selling the UNIVAC. Olivetti had transistorized mainframes before IBM. I think the interesting question is why IBM survived while the rest didn't. My highly oversimplified answer would be the IBM 360 crushed them.
