The Big Bang theory, like many technical and scientific advances, was something whose time had come. 

https://en.wikipedia.org/wiki/Vesto_Slipher

https://en.wikipedia.org/wiki/Carl_Wilhelm_Wirtz

https://en.wikipedia.org/wiki/Edwin_Hubble

https://en.wikipedia.org/wiki/Alexander_Friedmann

Einstein's General Relativity does not support a static universe. Lemaitre followed up on that, after others did.