Seems to me this will forever remain a mystery, in the absence of a CVR. It's beyond comprehension how an experienced and by all accounts excellent pilot could have (a) ignored multiple low fuel warnings (b) forgotten to turn the transfer pumps back on and then (c) when the inevitable happened, failed to enter autorotation, for which you'd expect him to be spring-loaded considering the fuel situation.
It makes me think of some classic rail accidents where the driver's actions are just beyond comprehension: Moorgate in 1975, or Grantham in 1906 (where the driver was seen calmly staring ahead, travelling at full speed into a low speed curve).