Humans have been inventing gods since agriculture began, if not from before. There is evidence that ritual burial of the dead extends as far back as 100,000 years or so. What the belief system behind those burial rituals was, we can only guess. It was only with the advent of agriculture and the emergence of population centres in what is called the Neolithic Revolution, that religion became more organised, especially when political leaders understood the value of being able to claim divine authority. Given that the Neolithic Revolution occurred in several places at roughly the same time (at about the end of the last glacial episode), different religions developed in different places, and each of these religions had its own god or gods. Most, if not all of the believers belonging to each of these religions would have been adamant that their religion was the one true religion and that their god (or gods) was (were) the one (or many) true god (or gods). This has not changed.
So, when you talk to a christian, a muslim, a jew, a hindu or a sikh, among many others, you need to realise that they don’t believe in almost as many gods as atheists. An atheist feels the same way about the christian god as your average christian feels about Thor, Zeus, Osiris, Jupiter, Vishnu etc.
Each civilisation believes in its god or gods just as fervently as christians believe in theirs. However, when you listen to a fervent christian talk about their god or Jesus, you would think that no other gods exist or have ever existed. So what do these christians think about these other gods that earlier or other current religionists believe? An acquaintance asked this question of a friend of hers, who happens to be an enthusiastic christian, and phrased it thus: ‘So, you believe that all other religions, other than yours, have got it wrong?’ His reply was simply an unqualified: ‘Yes’.
To me, this indicates he believes that all these other gods, to whom people prayed and made sacrifices (sometimes human) so enthusiastically, were imaginary. That is, that they were figments of their believers’ imaginations. That they did not exist. If this is so, how could all these believers have been so easily misled? If these billions of believers were so easily misled, how is it that christians can be certain they are not being misled?