Sorry but ... You installed OBIEE 12c, during install you created the required DB objects (using RCU or implicitly during the config procedure) and all was ok.
Then at some point you decided to take the RCU and drop the created schemas.
After that with RCU again you created it again using the same prefix (so same schema names).
And now you are asking why your OBIEE doesn't start anymore?
(just to be sure to clearly understand what you did)
If it's what you did ... where you expecting something else?
The RCU create the schemas and tables etc., but the config process of OBIEE insert content into these schemas.
So when you dropped it and then recreate you deleted all the data the config tool inserted.
Read what Gianni wrote and make sure you understand what mistake you made. Then uninstall OBIEE and reinstall it and be sure to not repeat the same mistake.
Thanks Guys. Learned the lesson. I used to do the same in 11G version.