The article you linked makes no mention whatsoever of the oil being special in any way. Quick googling says it’s just crude that is high in sulfur and lower in gravity. So basically it’s a slightly cleaner version of the lower grades, nothing coveted or specifically sought after.
Meanwhile, your own article mentions that the lifting of sanctions is in direct response to election reforms and predicated upon further action to allow free elections and release political prisoners. Per your own source, the reason for the change is to encourage less dictator like actions and not US demand for their specific oil.