Somebody mentioned that there were two aircraft holding who had come from BCN which was the alternate for the BY flight. This must have greatly increased the "must land" mentality as with your alternate out as well your options are fading fast. The selection of BCN as an alternate was highly questionable given the fx. weather for all the airfields along the coast. I was flying in southern Spain that night and had Madrid fuel up my sleeve (ie. a lot of extra) plus enough to hold at our destination for 45 minutes before diverting. In the end we didn't need it but the weather was really bad all along the coastal area that night and knowing I had enough to divert well inland was a nice feeling. I can remember the details pretty clearly because I read about the BY accident the next morning over breakfast and like many here thanked my lucky stars it wasn't me. I took lots of extra that night but it's quite possible the implications of the forecast weather could have got past me and I would have departed with less fuel than we really needed which is maybe what happened to these guys. I am sure that had it dawned on them that their alternate and most of the other airfields in the area could all go down as well then they would have nominated another one.
It's very easy to scan through the weather pack at briefing without building up a picture of whats going on and what the implications of the information are and I must say that this accident plus a situation I got myself into at the start of my time in the left seat have made me much more carefull when looking at the weather, even on seemingly benign days.