The Nautilus Pullover was the first Nautilus machine developed by Arthur Jones. He wanted fully isolate the lats because he felt the biceps, forearms/grip were the weak links in traditional pulling movements done for lats/back. The lats are such a large muscle group compare to the biceps so the biceps would fail first before make deep inroads into the lats. If you remember, the original pullover was coupled with a pull down so you could do pre exhaust with the pullover and go immediately to the pull down.
It fell out of favor because most people simply did it wrong. They would pull with their hands rather than drive with their elbows defeating the purpose of the machine. I use to dispense even touching the bar with my hands and just position my elbows on the pad and just keep my arms bent at a 90 degree angle and just drive with my elbows. This movement mimicked the front under grip pull down except full range of motion, your elbows would stretch back to behind your ears and go down all the way to your waist. No arms. Just pure lats.
He also developed another brilliant piece that mimicked the traditional front wide grip pull down except, again, the resistance was on the elbows/upper arms (by passing the biceps) and again a full range of motion. Twice the range than the traditional pulldown as your bicep would press against your ears and go down to your waist.
Again, it fell out of favor as most had to taught how to use it correctly therefore most used it wrong.
Jones was a genius.
