Think it was combination of both, not solely on his defensive contribution in that WC. I disagree on the notion he didn't advance all that much. Of course he wasn't a wing back in the South American terms, but it is natural since France played in a back 4 so he had to be a balanced full back and the team relied both in him supporting the attack and being solid at the back.
Karembeau only featured in about game in a half or something, remember he didn't feature all that much and France's solidity at the back was highlighted by Deschamps sitting in front of the defence and having industrious CM ahead of him also protecting the back 4.
Thought both him and Lizarazu were excellent going forward and providing that balance in the team with a lot of supporting cast and team players like Guivarch, Diomande, Boghossian and Karembeau all featuring at some stage.
Thuram was excellent going forward not only against Croatia, but also against Italy, Paraguay and even in the final from what I remember. It obviously needed him to tuck in at some phases during the games as Desailly and Blanc? were send off in the knockout stages.
Obviously being at the RCB is great fit for him in terms of peak level and that's his best position, but IMO that's more at club level or the 2006 WC as Raees mentioned. I thought you guys would go with Djalma from the off as he is technically brilliant and perfect fit for 3-5-2 RCB position.
But better leave it for the games as they are bound to be very interesting.