Using slow movement to capture fast moving prey would not be adaptive for a carnivore--you need to consider energy needs vs energy expended.
Suppose the meat at the meat market was always moving around the store to stay away from customers (you) and you only ate meat and moved very slow. How long before the lettuce looked inviting ? Recall that carnivores are "flesh" eaters, modern day species include mammals (cats, dogs, wolf, lion, tiger, coyote), reptiles (alligator, Komono dragon--a lizard), fish (shark). Since slow moving carnivores are unknown in present time, no reason to expect they were present in dinosaurs.