I think he was mostly chosen because like Fleming, Faulks is really good with writing about locations.
Yes, he is. Pick up A FOOL'S ALPHABET for more proof of his excellence at bringing locations to life. This novel (from 1992, I think) also contains some strikingly Flemingian passages, to the point where you could change the main character's name and believe you were reading extracts from a Fleming Bond novel. Although I wonder whether anyone at IFP even noticed that.
But why - precisely - was Faulks chosen? Well, he's a superb, versatile, critically acclaimed and bestselling writer with a proven gift for pastiche who's also fairly young and media-friendly. He's kind of like the Marc Forster of British literature, i.e. a respected rising star with a few hits under his belt - as Ellis in DIE HARD would say, he's happening.
But that may not be why he was chosen. For all we know, he got the gig because he and/or his agent is friendly with someone at IFP. The old boy network, in other words. He may have been chatting about Fleming during a conversation at some literary establishment luncheon and afterwards someone buttonholed him and said "I say, I wonder whether you might be interested in....". In other words, his selection may just have been one of those happy accidents.
On the other hand, perhaps IFP were actively looking for another "Amis type" who'd pen another COLONEL SUN, and felt that Faulks was the sort of author who fitted the bill.
Who knows?
