Well, maybe not, but most of the big ones are at least mutually exclusive. So to the OP's point, at various periods throughout history at least ~80% of the population were "believing false things", even if we can't agree on which 80% those were.

To the extent they can be, yes.

Whether or not a certain religion is "proven false" is generally not a productive question. But many religious people would proudly state that they would continue to hold whatever sacred belief they have even if it were proven wrong. So I think the popularity of religion does show that people want to believe false things, regardless of whether the religion is true or false or (most commonly) unfalsifiable.