I think Newton didn't make it because early 90s jet setters liked Palm Pilots that would fit in your pocket and played well with non-Apple computers. It was pretty rare to go to a meeting and see a Newton, but everyone would pull out the Palm Pilot. Price and form factor were probably the drivers.
Newtons predated the Palm Pilot by a couple years. The Pilot 1000 was not released until 1996. The Newton was on the way out by the time the Palm Pilot was released and off the market by the time the really popular Palm III/V/VII series was released. So in the early 90s no one had a Pilot and by the late 90s the Newton was history.
The jetsetters the Newton was targeting (or I posit they were targeting) did end up getting Palm Pilots in the late 90s but in the early 90s likely either went with electronic organizers like a Sharp Wizard or a full laptop if they went with any electronic PIM/organizer device.
