Affiliate Marketing Secrets

First of all, I am only asking this question about true dinosaurs. I am aware of, but not asking about: Pelycosaurs, which lived before the dinosaurs; or Crocodilians, which lived before, with, and after them, etc…. It seems that every purely carnivorous dinosaur fossil we have found has been a two-legged Therapod. We have found bipedal herbivorous dinosaurs, but no quadrupedal carnosaurs. Is there a theory as to a reason behind this? Were Therapods simply first and “guarded their niche” successfully, or is there a good reason why a quadrupedal carnosaur wouldn’t be successful. Or, is it simply that we haven’t found their fossils yet?