Nationalism vs Religion

That is a sign that Badr sectarian militias are not doing well against the sectarian militia of Muqtada As-Sadr. Both groups are Shi'ite and are funded by the Islamic Republic. So, you ask what does Iran get out of turning one shi'ite group against the other??

Answer: Both groups are Shiites just like most of Iranians. Yet,unlike Iranians,
both are Arabs too.Lest any of them feel too powerful and take an Arab stand instead of a Shiite one,inter-fighting amongst makes both much weaker and thus more dependent on Iran.