There were indeed very few Sicilians and surprisingly, only one Nadorf game. Why?
At their level, preparation plays a huge role. Unlike the ancient, more positional and well-worn waters of the Ruy Lopez, very sharp novelties are more likely to be found in the Siclian. The Najdorf itself was only invented in the 20th century. In addition, given the oposite castling situation, it's also more likely that novelties will be deadly. White also has freer play and thus more scope for decent if objectively frowned upon ideas, like the Freak Attack. The Sicilian is a battle of two plans and not so much with immediate direct contact and with the purpse of just stopping White's aggression. Many GMs. unlike Kasparov, weren't confident to walk on the slippery grounds of the Sicilians, even if the Sicilian is completely sound.
Another related reason is that openings like the Sicilian are in many ways all or nothing. The result will be a win or a loss and rarely a draw. While the winning chance for Black also increases, White is still more likely to win in most variations. This is especially true at their level where White's initiative and first move advantage can be nurtured for a long time. The chances of a draw in the Ruy Lopez and associated openngs is much higher. In a round robin tournament, a loss as Black could be quite costly and so they felt this was a better percentage play. Draw with Black, win with White when you actually have a comfortable, if slight edge, or at least a better chance to direct the game's nature. I don't agree with this approach, but I guess they feel it suits them best. It certainly isn't so at the less than 2200 level.
BTW: Anand handled Morozevich's e5 Najdorf well. This was less challenging because, Moro played an inferior, but more strategic line. It would have been better to have Rxc3 after Qf2, instead of Nc4. However, what really lost the game is Morozevich's overagression, where he sacrificed both central pawns. In any case, the Sicilian didn't do partcularly well this tournament and was played very rarely.