In college, when I was still struggling with letting go of religion, I reasoned with myself that most religions were either born from the same source or out of greed (like scientology). I took a class that analyzed ancient myths and modern religions, and one thing we discussed was how every religion that came from the fertile crescent has a "flood destroyed the world and humans have to repopulate" story. Religions not from that region were less likely to have flood stories - because other regions didn't have seasonal flooding.

It's very easy to have a case of "deities/deity gave vague information and that split into many religions, all of which are rooted in validity."

I also saw someone mention polytheistic religions treating others as equally valid, which is also a way for multiple religions to all be right, and one I hadn't considered but now really want to try. Their deities or spirits or sprites are for their region and are all valid. There could even be cross religion interaction between deities in that option (if the religions are actually really real and interact with humans).

We didn't always live in a world where the prevailing religions treated their deity as "the one to rule them all!!" There's many ways multiple religions could all be valid when you break from that mindset.