What were popular theories of the universe's creation before the Big Bang Theory was conceptualized?
The first theories were from theology: the universe was created by God and it is static with the Earth in the center.
There were no measurement to support this idea, it was based on purely speculation.
Even with Newton gravitational theory there wasn't a proper cosmological theory. This is somehow surprising because the theory of Newton consider the gravity as purely attractive force, so the concept of a static universe isn't simple to imagine in a universe dominated by an attractive force.
The first scientific cosmological model was given by Einstein. He used his equations of gravity (general relativity) to estimate the evolution of the universe. And he discovered that a static universe was an unstable solution, so he modified his equations adding the cosmological constant in order to have a static universe.
Even Einstein didn't think about the possibility to have a dynamic universe.
The first person that changed this old vision was Hubble that measured the velocity of expansion.
When Einstein read the results of Hubble he said that he was not clever in changing the equations adding the cosmological constant. He should have considered the possibility of an expanding universe.
Now we know that the universe expands and it is also accelerating with something that we do not know (we call it dark energy).