Originally, bitRUB was supposed to be the on-chain counterpart for RUB. bitRUB was globally settled soon after the chain started. Since there was no way to revive it back then, someone created bitRUBLE as a replacement.
Now that bitRUB has been revived we have two bitassets for bitRUBLE, which is unfortunate of course. It's up to the users which asset they use, and up to the feed producers which asset(s) they feed.