While it would be nice to think incapacitation is involved, there is no evidence for it. We can speculate as much as we want, but it is worth remembering that history is littered with accidents where unstable approaches have been continued with disastrous results.
Some, like the Air India Express accident at Bangalore and the Learjet overrun at Northolt (2 pilots, same sort of private flight) were excursions resulting from long and hot landings - the Learjet was 30-40 kts fast on bug speed at touchdown. Others have turned into CFIT accidents through missing the runway entirely in VMC. The Birmingham UPS A300 accidents hit the ground a mile short even though the crew had seen the runway.
The common thread is people persisting with a flawed mental model when all the indications should have been telling them to chuck the approach away and start again. Incapacitation is extremely rare, and I suspect incapacitation on the late stages of an approach is rarer still.