There's no blame game. Iran have accepted it's their fault. They may be trying to cite other external factors but they have owned up. I don't think the average joe would understand the internal turmoil an event like this would bring to Iran. There exists a system Vali-ye faqih (Guardian Jurist). This is more so in Iran (khomeni) vs Iraq (sistani). The Iran has a democratically selected government however it's actions are overseen by The Ayatullah to ensure it is in line with Islamic ethics. To simplify. An event like this would have the nationalists denying everything. Once the truth comes out Islamically the dead are owed compensation, apology and the guilty trialled. Remember that the different Ayatullah are Pope figures to people not only in Iran but across the world (shia and some non shia). They can easily lose credibility depending on their responses. You can now see the head of state Rouhani mentioning all of the above.