I find it difficult to accept the lighting fixture falling was the main reason for Alonso's lack of pace. Whenever that happens, the mechanics immediately check for damage, put the car up on jigs and check all dimensional tolerances to see if anythign was knocked out of alignment. And they fix it befor ethe car is released from the garage.
My reasoning was that this incident set the tone for the entire day, that Alonso suffered one of his rare days when he didn't bring his entire game.