People in a rollercoaster or falling elevator feel the rapid descent, so why don't pilots in the cockpit?
You only feel the acceleration downward. In roller-coaster this sensation is maximized for maximum thrill. A stall isn't instant: some parts of the wing can be stalled while the rest still provides proper lift. Once the airplane is near or at terminal velocity in a stall it will feel no different from regular straight and level flight.

The onset of the stall was paired with some turbulence which would mask the downward acceleration.

Pilots are also trained to ignore their own sensations because they can be misleading leading to spatial disorientation. You can be in a spiraling dive and still feel as if you are flying straight and level.