Most Physics, Biology and Astronomy knowledge we have acquired in the 19th and 20th centuries that have repeatedly shown us that human beings are not at the center of anything, and our subjective bias in explaining the world around us has to be filtered out when we try to discover the laws of the universe.
Existentialism is self-centered, ego driven and too focused on emotional gratification and other trivial psychological drives. It can’t really explain anything of importance.