The 286 was "brain damaged" for implementing operating systems according to Bill Gates for two reasons: (1) you could not get back to real mode without doing a terrible hack resetting the whole machine, (2) you could not write to segment registers at all from user mode so writing programs that use more than a 64k data segment and 64 k code segment means doing an OS call.
The 386 on the other hand took forever to get to the point where a 32-bit OS was mainstream, from 1985 release of the 386 to 1995. Some of us (me) were using Linux before then, but that was it.
My conclusion about the 286 being pivotal came from my own experience (switched in 1987) and also looking at old issues of Byte magazine circa 1987 and seeing that all the advertisers were in a state of turmoil. For instance some firms like Cromeco who sold S-100 bus and CP/M machines to OEM's to put, say, a cash register system in a supermarket were giving up the ghost because PC's were crushing them. Similarly there were ads for PC clone makers all over the place but anything associated with the 8-bits was vanished. The original IBM PC was much more expensive than 8-bit machines but not much better in terms of power, PC AT clones were still more expensive but they were so much more powerful that it was worth it.