Before this discovery, Alexander Friedmann had made two theoretical assumptions. One was that the Universe looks identical in whichever direction we look, and second, this would be true if we were observing the Universe from anywhere else. Therefore, since the noise appeared to be same in different directions, the Universe must be the same in every direction, on a large scale. Thus, Penzias and Wilson had stumbled on an extraordinary accurate confirmation of Friedmann's first assumption.
There was also speculation that the early universe should have been white hot and dense. Many scientists argued that we should still be able to see this glow as light from very distant parts of the early Universe should be reaching us now. But due to the redshift, this light should appear as microwave radiation. And this radiation is exactly what Penzias and Wilson found!