Anecdotally it seemed very popular, and loved by the people who bought one. Perhaps the numbers said otherwise, because otherwise I have no idea why they didn't reintroduce it as an M1/M2 machine.
Perhaps, and this is maybe just being hopeful, they're waiting for the even better efficiency of the M3 etc before reintroducing it because they want to do it, but absolutely nail it when they do without any battery life compromise. After all, they already ran the market demand test, so this would make sense if so. If that turns out to be the case I'll almost certainly buy one.
I loved mine, and put a couple of hundred thousand miles in carrying it (even wrote a lot of code in Emacs, but I remember the days when every compile was an excuse to stand up and get coffee, so the speed didn't matter to me).
AFAICT its target market was actually Asia, same as with the ultralight (for its time) Powerbook 2400c which was actually built by IBM Japan. But it didn't sell as well as expected even there.
Here are their sizes for comparison:
MacBook Air 11" 300 mm x 192 mm x 17 mm 1,08kg
MacBook 12" 280,4 mm x 196,6 mm x 13,2 mm 0,92kg