It is very hard to give details in a brief comment. It is certain that many converted out of genuine belief in the Christian god. That does not change the fact that converting from one religion to another was not without reasoning. There is myriad reasons but the general take on my comment is accurate. And it was quite common when visiting other cities to pay respect to the god(s) of that city in the pagan world. This is why many victories would involve desecrating or stealing the religious idols contained in the defeated city’s temples. Even if that city’s god was not your god, seizing the physical nature of the god was seen as a good thing as it enhanced your power and hurt your enemy.
They stole the other parties' gods to prove that their gods were superior or true and the other gods were inferior or nonexistent. For example, see
Sennacherib's destruction of Babylon's temples and the replacement of Marduk with Ashur as the spiritual backbone of the neo-asyrian dynasty. Liekwise the babylonian destruction of the first temple, or the Roman destruction fo the second temple.
The trade routes in ancient times were advanced, as well as communication channels. As Egypt traded with other kingdoms and also intermarried, they respected each others’ gods. I reiterate that the Christian attitude towards other gods was different than the pagan attitude, where even within the same religion many gods existed.
