John the only thing missing from the above explanations is that an aircraft has an unique drag curve, its U shaped as opposed to straight line as to say your car.
Swept back wing aircraft normally approach on what is called the wrong side of the drag curve and are therefore speed unstable Eg any reduction in airspeed increases drag even more causing a further speed loss.(this is a product of this UNIQUE drag curve)
Any aircraft with wings can glide to land but to make a safe speed stable approach in a swept back wing aircraft you need the assistance of thrust.
Once the aircraft has intercepted the ILS glidepath it is on course for a touchdown point 300 metres from the threshold on what is normally a 3 degree glide path which is around 300 feet for every mile out from touch down. EG 2 miles at about 600 feet above aerodrome level. In the latter stages of the approach more drag producing flaps and undercarriage will be lowered which basically means more thrust will need to be be added to maintain that glidepath. At around the normal height to have everything out and dangling and the speed correct, which is just inside 2 miles the aircraft is very thrust dependant so if you take any thrust away at this point the aircraft cannot maintain that glide path and will land short. However you have got one other workable option of some free energy and that is the excess airspeed above the stalling speed. Aircraft approach at a safe margin above the stall speed and it it is this margin that allowed this aircraft to limp onto the airfield. The pilot used this margin to modify the glidepath to get to the airfield but there obviously wasnt enough spare airspeed to maintain the correct 3 degree glidepath.This very abnormally slow airspeed also contributed to the low ground roll out of the aircraft after touchdown. If the gear had been raised the aircraft energy would probably not have been as effectively removed as it was on touchdown.