Once again Lemaitre and Planck's theories were considered faith based at one time also- arguably a pretty productive basis as it turns out!
But can we at least agree to put all that aside- that we should follow the evidence wherever it leads- no matter the implications of it?
aka the scientific method, or how would you define that?
Once again, you are completely ignoring that Lemaître did not contribute to the expanding universe model (later the Big Bang model), nor was he the earliest.
The Russian theoretical physicist, Alexander Friedmann, thought of it, in 1922, 5 years before Lemaître's Hypothesis of the Primeval Atom (1927).
And also 2 years before Lemaître, in 1925, the American physicist, Howard Percy Robertson, came up with his own expanding universe model, as well as predicting using the redshift to determine if the galaxies were moving away from each other, which Edwin Hubble confirmed in 1929.
All 3 physicists had independently predicted the expanding universe model, using General Relativity as the framework for their respective models.
What is remarkable that such ideas came so soon after Hubble using the Hooker Telescope, that the Milky Way is only just one of many other galaxies out there. The discoveries that the Andromeda and Triangulum galaxie, not nebulae, separate from the Milky Way, was observable evidences that the universe was much larger than the Milky Way.
Friedmann, Robertson and Hubble were the earliest advocates for expanding universe model, not just Lemaître, and they are 3 known atheists.
But the expanding universe model or the Big Bang model isn't about theism vs atheism, it was just physics and astronomy. It had nothing to do with one man's religion or God; it was just about the science.
Lemaître was an important contributor to the BB model, but so were Friedmann, Robertson and Arthur Geoffrey Walker (Robertson's partner in the 1930s).
And in 1948, George Gamow, Ralph Alpher and Robert Herman were responsible for extending the Big Bang further than Lemaître, with the Hot Big Bang model, the Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background Radiation (CMBR).
Without Gamow and Alpher, Lemaître's model would have become stagnant. CMBR was the biggest evidence of the universe expanding, from a hotter and denser beginning. It (CMBR) was not discovered until 1964 by Arno Penzias and Robert Wilson.
Albert Einstein actually didn't like Lemaître's model (1927), and came up with his own cosmology model (spherical and static universe). Brilliant as Einstein was, It was Robertson's peer review that made Einstein withdrew his model.
You shouldn't ignore history, as you have repeatedly done,
@Guy Threepwood .