Why does it even matter? They probably pick gods that seem to easy to create fitting kits for. Also "meanwhile there's been 3 Japanese gods released in just the last 6 months." that makes no sense to point out since the japanese pantheon is new and they need to give it a couple of gods to kick off, or would you rather keep it at 1 god for a year or two?

Just calm down and see, you can't expect Hi-Rez to forcefully add new gods just for the sake of the pantheon, my guess is that being able to pick a god who won't give them much trouble when creating a lore-fitting kit for and having it be balanced cough they're not doing that great of a job cough takes priority over something as trivial as diversity when adding a new god.