As stated during the broadcast, a possibility for MS lockup could have been that there was more rubber "marbles" in the racing like from Alonso's earlier pass attempt. When MS hit the brakes hard to keep them warm, the left font might have been on some of this debris and subsequently locked inadvertantly. MS made a bad decision in my opinion to try that in the tunnel at that moment, but it his hardly all his fault. JPM was following closely and you can see his reaction was not to slow down, but to try and speed past, even though passing is absolutely unconditionally not allowed when the pace car is out. Even so, as the steward said, it's is not fully his fault either. Quite an interesting turn of events, quite amazing to see it live.
An interesting thought.... Imagine if the roles were reversed, with JPM locking up and MS trying to pass and colliding. I would bet the post race drama would have been a LOT more intense if it was JPM who felt that MS was the reason for the incident. I'm not really taking any one drivers side, but I think it is admirable how MS doesn't let his emotions effect him nearly as much as many other drivers, especially JPM. If JPM could control his emotions a bit better, I think he has every bit a chance to be as good as the best drivers ever. As shown, when on his own, he is arguable the best qualifying driver out there, but in race situations, I wish he didnt get so upset and take such risks.
In either case, AWESOME to see all the main teams either eliminated or severely handicapped and the smaller teams battling it out. One of the most amazing races in recent history if you ask me.
Just my $.02