Ok what is up with MiHoYo focusing so much on mushrooms for Sumeru? It's not like Persia is known for their fungi right? 
You've gotta be kiddi-
As it turns out (and I'm not sure how big this is since looking up "mushrooms" and "Persian mythology" is the only time I got this information) mushrooms were not only central to Zoroastrianism but also Christianity. Go figure! 
So once upon a time Zarathustra needed to purify the waters in order to receive revelation. The Yazata Haoma a spirit under the Ahura Mazda (God in Zoroastrianism) appeared before him and helped him do it and for that he was made the first priest of the Amesha Spenta. Funny enough though the priest is not venerated in Zoroastrianism and has since fallen from grace.
I'll get to that part in a second but since this was about mushrooms what does any of this have to do with mushrooms? Yazata Haoma was a divine spirit but there's actually a thing called haoma which was an herb used in religious practices. What was this herb? Well one of the abilities of haoma when taken was to cause hallucinations. Gee I wonder what "plants" we meme about that cause hallucinations.
According to a 2010 archaeological discovery there was a rug found in a Xiongnu (Hun) burial chamber. The design on it showed how the people depicted were using the haoma in rituals. It was specific enough that archaeologists were able to possibly identify what the haoma was and they claimed it was either of 2 species of shrooms lol.
Going back to the religion we have another story this time about Zarathustra's dad. Apparently he put a haoma into milk that he gave his wife and that's when they conceived him. Apparently by doing this the haoma's spirit was placed inside of Zarathustra. Also when he was purifying the waters he said this: "These offerings, possessing haoma, possessing milk, possessing pomegranate, shall compensate thee."
Ok but then why is a divine spirit and divine plant the inspiration for a bunch of mushroom monsters in Sumeru? Well Yazata Haoma as priest was affiliated with the Wahman. Remember what I said about them? If the story goes that way then Yazata Haoma is affiliated with the branch of Academia that's causing the problems we're likely to resolve through the Archon Quest.
What if right now it's these Wahman who are focused on maintaining the Akasha System and getting themselves influenced by Dottore? What if these old practices of treating knowledge as currency are also the reason why they can't dream? (remember what Ei said dreams are?)
I doubt MiHoYo will actually have shrooms be a part of their game but symbolically this could be the tie-in. Since it is Yazata Haoma who affiliated with the Wahman, is related to the haoma shrooms and also fell from grace in real world mythology all of that adds up in Genshin as the shrooms being a problem for Sumeru aka monsters. And who knows? Maybe they're also like the Oceanids were to the original Hydro Archon. They were creations of Rukkhadevata and stand for the old Sumeru while we'll be bringing Sumeru into its new age.
Shroom lore. Who knew? 
Tips and Tricks from a Super Casual Genshin f2p
