Bash first came out in 1989, but the typical shell of the time was sh, and it ran on Unix systems with more memory, storage, and CPU power than the typical PC. Thus it's no surprise that the sh family started with more features, while COMMAND which cmd evolved from was extremely minimalistic. DOS 1.0's COMMAND.COM was just slightly more than 3 kilobytes and didn't have conditional nor goto statements:
Even if the *nix machine was no bigger than a PC (e.g. - Xenix on '286; BSD on a PDP-11), it could still swap out processes, vs sharing a single real memory space.
But as you said, this allowed (at least the illusion, on some machines) more total memory to work with.
In the 1980's a 80286 would have been toward the high end of x86 systems. The 80386 started shipping in bulk in 1986 and the Compaq DeskPro 386 and IBM PS/2 Model 80 were well north of $5000 in 1987 and the "prosumer" PS/2 was the Model 60 with a 80286 when the line was released.
Even in the late 1980's 8088 based systems were pretty typical and why IBM included the PS/2 25 and 30 in its initial product line.
I remember using (sharing!) an XT (8088? 8086???) at work in 1985. One good thing about the 386 in 1986 was that it made the price of 286 (AT/clone) systems come down. I almost never saw an XT after 1986. We started seeing quite a few more clones (Compaq, etc) about that time, as well.
Which is of course a big tangent off of "why/whence command.com & .BAT files" :-)
OS/2 and Windows were a big deal in virtualizing memory use in PC land, with widespread Linux use still "a few years" in the future. (and effective adoption of NextStep even further out)
I think the 80386SX was also a factor in lower 80286 prices after the 386DX came out. Those systems were really popular.
When I bought the Amiga 500 in 1988, 8088 Turbo machines were still the entry level clone system. My vague recollection of the consumer and small business market was that that obtained for a couple of more years.
http://www.os2museum.com/wp/dos/dos-1-0-and-1-1/dos-1-0-dir/
http://www.os2museum.com/wp/dos/dos-1-0-and-1-1/