Can someone tell me what "Condition" is? Is that like prop pitch or something?
Yes, related to prop pitch.
The condition levers set the propellor speed - which does not directly relate to thrust. When moved forward, the condition levers cause the prop pitch angles to decrease, resulting in an increase in rpm, but no increase in power unless the power levers are also advanced.
As the crew intercepted the LOC, the condition levers were placed full forward in preparation for landing (higher rpm available in case of a go-around.)
As someone noted earlier, the full-forward position of the condition levers with power at idle causes the propellors to function as 13.5' diameter discs -- LOTS of drag -- unless accompanied by an increase in power lever position.
The airspeed decayed pretty rapidly; it was astounding to watch the red bricks of the airspeed tape's low speed cue rise up with no action whatsoever by the pilot.
The power was never increased until after the stick-shaker fired; apparently indicating sudden crew surprise at the loss of airspeed.