I grew up Mormon and had a hard time believing that we were the "true church," "taught the true teachings.," etc., when I learned about how many different current and old religions and beliefs people had throughout human history. Cracks started to form in my faith foundation then. The following thoughts throw me for a loop back then. Exibit A. Exibit B. Exibit C.
There are over 40,000 sects of christianity last I knew. I'm going to say thousands isn't an overexageration. I won't consider religions the same if they have different beliefs.
Part of it is probably what determines what counts as “a religion.” My mind went to indigenous groups in the Americas, Australia, and Africa - thousands seems appropriate there!
Historically, religions as practiced on the ground were very syncretistic - like in the late medieval Muslim world, a Christian might carry a verse from the Koran as a charm or Muslim might visit a rabbi. Not to say that there wasn’t religious persecution and attempts by religious authorities to make sure that everyone was following the rules, but the species of religious fundamentalism we see today is a product of the 19th century and widespread literacy.
Even within a modern Protestant church of a specific denomination, there’s probably a mix of people who are universalists, into spiritualism, etc.
I don’t really think religions can be considered discrete in a way that one could report “there are X religions in the world.”
I wasn't able to find Babi, but did find Bahai and Mormon in the tree. I don't have the time right now to try to find the others, but I'm going to guess that they're in there or didn't make the cut when making the tree.
Do you happen to know where a higher resolution version of this image is?
I am not very knowledgeable about religion but that chart buckets European Animism as one "Religion" while I think it was not organized and refers to the disparate beliefs of folks in the area at the time, so one could argue that there were lots of version I think.