Nobody said he did a major part of the work “by himself”. The vision however was completely his own and you should know he fought for Apple to have its own internal hardware.
Oh yet another gospel of messianic St. Steve founded on the rock of revisionist history.
Apple has sold hardware at the aggregate level from the beginning. In the broadest sense , yes they have had "internal" hardware where there some was Apple contribution to the design. That doesn't mean they have made all of the major components .
In the original vision Jobs wanted all the hardware inside a Mac to be designed and controlled by Apple.
You mean like the time Jobs dismissed using the Sony 3.5" drive for the Mac (too expensive) and the hardware team had to hide the Sony guy whenever Jobs came to visit the lab because that was the more prudent viable option. Finally, after Steve admitted that they didn't have a viable option for the Mac storage drive and that they needed to discuss what viable options they could do at that late in the product development cycle, the team reveals to Steve they never got rid of the Sony option at all and it is about ready. That purely Steve's vision of the Mac?
Nevermind that Jef Raskin created the Mac Project and Jobs took it over. Jobs didn't even come up with the name "Macintosh". That complete vision, right? *cough*. ( Or one of those folks who believe that Musk founded Tesla? Not. ) .
Jobs 'vision" was more in slecting the correct team to do the product than in the required necessary details to do the project itself. Hiring folks who would ignore him if he was going down a deeply flawed rabbit hole was more important than being supreme vision dictator.
Even after he left Apple in the mid-80s Apple continued to understand the importance of this and invested in ARM around 1989-1990.
Steve isn't there but it is still purely
completely just his vision. Yeah ... right. Acorn founded the Arm initiative. Apple came in and provided some money (not 'vision') to get it off the ground.
At NeXT Jobs believes the Mach kernel and OpenSTEP/NeXTSTEP should be portable.
The created at Carnegie Mellon Mach kernel ? Steve's vision? Richard Rashid and Avie Tevanian have no "Steve Jobs" in their names. Steve Jobs hired Tevanian to work at NeXT but Steve didn't give him the portability vision for Mach.
Mach used a mutatted BSD Unix to bootstrap itself into a viable 'microkernel'. NeXT needed a Unix to be a viable university research workstation. There is no 'vision' there; it is was a common known basic requirement. (e.g., Project Athena found at MIT in 1983 (before the Mac launch, basically was Unix workstations with X Windows in a university setting). Being primarily BSD licensed Mach didn't get into expensive (for a limited fund start up) AT&T System V entanglements. Apollo , Sun and a couple of other research workstation contemporaries were all on the same Unix baseline approach in 1983-1985 timeframe.
The object-oriented framework structure for NeXTStep library layer was grounded in Objective C which also had totally exterior to Steve Jobs foundation. NeXt licensed Objective-C.
DisplayPostscript ... again started off at Adobe and became a NeXT joint venture... Jobs the core visionary at the beginning solely driving it? Nope.
It should be able to run on PowerPC, Intel (there was a build) and anything else that would come along in the future.
Initially NeXTSTEP was not portable. It was Motorola 68000 based (started at 68030 ). Mach was ported to other hardware platforms by other companies in 1985-90 timeframe by other entities before NeXT did. (IBM RT, Dev VAX , etc. )
NeXT thought about doing a Motorola 88000 but it didn't work out. Didn't do PowerPC (***). They did Intel, Sparc (Sun) , and PRISM (Apollo/HP). The big push to OpenStep was principally driven by when the NeXT hardware not getting substantive traction. Before NeXT founding there already were workstation vendors ( Apollo. 1980 Sun 1982 ). DEC shifted major focus into the area about when NeXT got founded. So the space was not uncrowded. Lots of folks had seen the Xero Alto ( and Lisa and a few other follow ons at that point.).
When macOS transitioned to Apple Silicon in 2020 you’ll remember in the presentation they said they had been working on it since the days when the iPad was first released.
And yet before the iPad and iPhone launched Jobs went to Intel and asked if they could make to chips for these products. Intel somewhat dismissed the iPhone but pitched an x86 something for the iPad. (Otellini is same goofball CEO that greenllit the Larrabee x86 GPU. The guy used 'x86' hammer on everything in sight. ). iPad project reportedly started before the iPhone did and yet the iPhone shipped first. Your assertion is that nobody on the iPad project knew the device was substantially underpowered but Steve. the only one with vision to see it? Probably not with any remotely competent team tasked with the job.
Blackberry already had a very successful Smartphone business with an Arm driven SoC. So it wasn't visionary at all to select an Arm solution for iPhone. Extremely unlikely that everyone else inside of Apple was cheerleading for a non Arm solution it is was solely Jobs who bravely choose the Arm path all by himself. In fact, the iPhone started off with a almost purely Samsung SoC.
The iPad didn't ship until Apple got to the A4 processor. If the iPad had been a problematic product then the transition to the Mac would have been greatly delayed. Yes Apple bought PA Semi in 2009 , but buying talent with money doesn't make you a 'visionary'. ( no more than VC's are not visionaries for the companies they invest in.)
Jobs have some impact on the path, but the completely solitary originator of the idea? Not.
P.S.
*** can hand wave that PowerPC was an effective substitute for Motorola 88000 , but more so the option Motorola chose to contribute to instead (PowerPC help to finish killing off the 88000) .