would it be fair to say that at the time of the dinosaurs the earths gravitational pull may have been less?

Question

only a hyperthetical, but this could explain why they were so big

Answer 1

A lot of accretion has happened in 65,000,000 years, but that alone probably does not account for the size of the dinosaurs. It is an interesting hypothesis, though, as some theorize that the elephant is an example of the largest sustainable land animal.