Help me understand why 我艹你 means i f*** you?
艹 -> 草 -> 操 -> 肏 all with pinyin "cao"

They're all Internet variants on the same word that proliferated through use of computer IMEs. 肏 (the proper character) didn't show up on some earlier IMEs, so 操 was chosen as an alternative for it. From there, 草 became used because it is often the first option that shows up on an IME when people are typing quickly (as is often the case especially in online gaming). From there, 艹 was chosen as a form of self-censorship that is somewhat common on Chinese Internet media.

There are other variants such as 卧槽.