https://www.computinghistory.org.uk/det/5424/Orb-Computer-Th...
- those with organic growth, where the sales of products financed the development of new products: MITS, IMSAI, Sphere, Ohio Scientific, SWTPC, Cromemco, Processor Technology, etc
- those that were part of a larger company: Radio Shack, Commodore, Texas Instruments and Atari-Warner
- those that were financed by venture capital: Apple
In retrospect, the companies in the first group were doomed to not become an Apple. Later on we got many more venture capital based computer companies, with Compaq among the most famous.
In the case of Sphere it had many more problems than just how it was financed. They got an early reputation for not delivering at all or shipping non working products.
What was special about Sphere was that from a technical point of view it was a generation ahead of the competition: with a built-in screen it was more like a Commodore Pet or a Radio Shack TRS-80 from 1977 than like the boxes with LEDs and toggle switches from its peers in 1975.
Personal Computers where an absolutely gold rush once people realised it was "going to be the next big thing" lots of companies had to have a Computing Division even if it seemed a bit weird for that company to have an AI division, oops my bad Computing Division.
In reality what happened was the vast majority of them went splat in short order and a handful of makers reached market in volume and once software started for the ones who did it became self re-enforcing - people wrote software for machines that sold well because they had good software.
In my era/part of the world the PC wasn't even a thing at home for most people until the mid 90's, if you had a computer at home in the late 80's/early 90's it was going to be a ZX Spectrum/C64 or if your parents had money Atari ST/Amiga.
It was an exciting time in the 80's (once I was old enough to use computers) because the world hadn't yet consolidated on PC/Apple *and everyone else* off in the margins.
Somewhat related, if you like this stuff or early computers, Halt and Catch Fire is an amazing TV show that nails computing in the 80's into the early 90's.