Yesterday I ate some old pizza that made me sick; 4 slices of hand tossed, chicken pizza from Pizza Hut. It was dehydrated and I used the microwave to soften it up. Until then, I kept it in the original box in my refrigerator. At the time I ate it, I did not see any visible evidence of mold or rot. I’m curious what happened to the pizza over this time that made it unhealthy to eat. Why?

I found a recipe online for buffalo chicken pizza. My only complaint is a soggy crust due to the bleu cheese. I tried a bit of olive oil on the crust to keep it from soaking through, but that doesn’t really seem to help. Any suggestions?
It’s bleu cheese dressing, btw, not crumbles.