“Religion was invented when the first con man met the first fool.”

― Mark Twain

Lol. In fairness though I think it's more likely that someone was overthinking their life and started having certain personal subjective experiences in their search for answers to what was, at that time, the unanswerable. And to make sense of all this they concocted beliefs that were consistent with those experiences and reproducible in others. And so religion was born. It's reasonable division of labor in a primitive hunter-gatherer society that a handful of persons would be supported to devote their personal time to furthering this inquiry into the nature of reality, and more practically, to provide at least faux comfort to the sick and afflicted.

In those early days I think freeloading was a self-limiting problem because of limited resources. If your shaman did not produce perceived results right in his own tribe, he'd be replaced. And it was a lot of work in its own right. Personally, I'd find being on 24/7 call to calm everyone's anxieties to be exhausting. It wouldn't be for everyone.

It's only here in the relatively affluent 21st century West where people have more money than sense, that lazy asshats can cynically manipulate people's native greed at sufficient scale to become wealthy, and get away with it.