Why do many people today worship one god and back then people worshipped many gods?

Answer 1

There could be several reasons for this:

You could look into Egyptian history to see the reason for monotheistic religions emerging out of a polytheistic one. A particular Egyptian ruler named Akhenaton has introduced the monotheistic concept to the Egyptian people during a time when civil loyalty was not as strong as Khufu or even Menkaure's time of rule. There is no one answer and the question may be quite unanswerable; however, you can try to find the clues during the transition from the High Classical to the Amarna period.

A similar contrast can be seen in Roman history when Constantine converts to Christianity and moves the Roman capital to Constantinople, which later embarks the Byzantine era.

If you want my opinion, I think that a monotheistic religion tends to bring a single deity to a more personal level and/or bring people under one deity, therefore creating a more organized mindset of the people. I think that this may have a lot to do with people's desire to get closer to the supernatural and it may also have something to do with the rulers' desires to get to know the commoners better. Nobody knows for sure. Perhaps when time machines get invented we could truly know for sure :)