the technical industry term we use for that is “life”. It happens to the best of 'em!
seriously, its the moisture from your sauce, toppings, cheese, penetrating the crust.
doing a archive search will give you some ideas, such as spreading a thin layer of oil on the dough skin before saucing it, or lowering the oven temp or increasing bake times to ensure you crust is thoroughly baked.
Try to repost with more details if you need better suggestions. Oven type, oven temp, bake time setting, pizza toppings most notorious for this behavior, etc.
Good luck!