The trouble is that you can’t separate your diet from other aspects of your health. Jorge mentioned stress, lack of rest and viral infections as potential factors in bringing about a candida overgrowth, and all of these are influenced by diet. Your diet shapes your gut flora, which largely shapes your immune system. Gene expression is also influenced by diet and lifestyle.
I don’t think the general public is at risk of candida on a Western diet, but not everybody on a Western diet is stupid enough to eat chocolate and pizza every day. There’s nothing “normal” about this, unless you happen to be a 12-year-old without your parents around. The food pyramid is a bad joke, but it at least set limits for people. If you aspire to live on junk, you’re going to end up with some disease or another, so who’d be surprised if it happened to be candida again?