After the Big Bang, what is the next most popular theory on the formation of the universe? What are some of the flaws in this theory? Why is the Big Bang the more accepted theory?

To put it mildly, the very definition of "theory" implies that an absolute proof does not exist; in the case of the early universe's development, this means that it will almost certainly always stay in the theory domain.

All the possible theories about what happened and how it happened are consistent with the known laws of physics, but the big bang theory is simply the best explanation for how the universe came into being at the beginning.

The big bang theory is currently the best explanation for how the universe began and why we are in this place, but it may not last forever.

After the Big Bang, the "Steady State Theory" is the next most popular theory explaining how the universe formed. However, this theory has several shortcomings, such as not being able to explain the observed cosmic microwave background radiation and not providing evidence for the continuous creation of matter. The Big Bang theory is more widely accepted because it is backed by multiple lines of evidence, including the abundance of light elements, the cosmic microwave background radiation, and the observed expansion of the universe. It has also been successful in predicting and explaining a number of phenomena observed in the cosmos.