The ancestor lizard had a very basic body plan for Dinosauriformes. Many of the earliest lizard to dinosaur transitional groups and genera were obligated to quadrupedality or at least facultatively bipedal. That was not for any specific reason except that the earliest forms of these animals were holding on to vestiges of the earliest lizards, probably some amphibious traits, and maybe even some of the traits that had been seen in pelycosaurs and mammal-like reptiles. The history leading up to these first Dinosauriformes has been difficult to trace and to suss out exactly. We have very good ideas and very well documented tranisitional fossils, but these do not answer all the questions, such as the one asked here; why do early Dinosauriformes tend to walk on four legs? Regardless of the actual answer, Asilisaurus kongwe is very clearly at home on four feet.