Serious question about Carter and the Iran-Hostage Crisis?

This is not a homework question, so I would appreciate serious answers. Do you think Carter deserves the blame for the length of the Iran-Hostage-Crisis, or was the situation beyond his control? I keep reading that Carter's "failure to react" to the crisis doomed Carter politically. However, consider this: he took immediate action by freezing billions of dollars of Iranian assets and did start secret negotiations. Do you think it is rightful to claim he simply couldn't get things done?