How do baking/cooking contests work ?

I have always wondered about companies that run baking/cooking contests.
They ask people to submit a recipe but how do they pick the finalists out of thousands of entries ? They couldn’t possibly try out all the recipes submitted to pick the top 10 to come in for the final bake/cook off to choose the winner ?
PS: I’m not referring to local contests but nationwide contests.
(Sara Lee,Duncan Hines,Pillsbury,,,,etc ,,etc.