The IRGC generals still look for legitimacy by pointing back at the role they played in defending Iran against Saddam Hussein's invading army during the 1980-1988 Iran-Iraq War. But Iran's conflict today is not comparable to the circumstances of the Iran-Iraq War.
Iran is bleeding today because there is a global economic sanction regime against it, backed by a strong international consensus.
Ayatollah Khamenei, certainly never a fan of the West or the United States, grasps the difference. That is why he conceded to the need for "heroic flexibility" and looking for ways to break the stalemate.
That is why Rouhani says he has the Supreme Leader's full backing to negotiate with the world. And unless the IRGC generals can come up with an alternative narrative for the way forward for Iran, then all they can do is sabotage Rouhani's efforts and hope that they can get away with it.