The cosmological Lemaître- Eddington model later became knick named "big bang" by Frederick Hoyle later, who apparently was reluctant to "believe" that the universe had a beginning point. It's commonly speculated that many of the physics community at that time disliked the idea as a statically existing universe was in vogue and that Lemaître was a Catholic priest caused Hoyle and others to deride the model as a "big bang" (with an underlying assumption that Lemaître assumed that God was the originator of why the expansion happened, see [1] pg 6). It's a bit unclear as to the exact thoughts of Lemaître and Hoyle, but there a good history on arrival [1].

So belief in the big bang affected the physicists who figured out the original cosmological model of the big bang and it took changing beliefs (based on evidence gained day the scientific method) for it to become accepted as a theory. Belief matters quite a bit. :)

[1]: http://arxiv.org/pdf/1301.0219.pdf

> Believing in Big Bang sounds just so wrong.

Why? Belief can be grounded in many things, faith, empirical evidence, etc. Even for an extreme version of empiricism-as-the-only-basis-of-knowledge, there is nothing wrong with belief, only with belief grounded in anything other than empiricism.