Were Dinosaurs Destined to Be Big? Testing Cope's Rule

A long time ago dinosaurs ruled the planet and were seen as the biggest creatures that existed. Then the Edward Cope made a rule that every creatures evolves to be bigger. This theory was tested to see if that actually happens by taking their thigh bone to see their size. They took the dinosaurs family tree and used that to see if they tend to increase in size which in most case we would think they would and they did. Although some of them didn't, the theropod dinosaurs evolved to be birds which made them smaller and have flat faces for better flight. There is also one option which disproved this theory and it was the famous t-Rex, how big could it get while staying bipedal since its tiny hands would almost never evolve to be big enough for him to walk on 4 legs.