I do not agree that the blame should fall on Syria/Assad, their allies were also fundamental to the downfall.
Strategic patience leads to strategic defeats
In 2017, at the first Astana meeting, the freezing of the conflict dealing with insurgent forces gave all possible possibilities for the military demobilization of the SAA and gave all possible possibilities for the flexibilization, reconstruction, support and modernization of the rebels, the responsibility for all this lies with Iran and the Russian Federation as guarantor of the agreement. Iran tried to discuss in a civilized manner with people who have no civility, with the consequence of these agreements leading to strategic defeat with the end of the Iran-Lebanon land link, the biggest strategic defeat since 1988.
Iran, due to its inertia or lack of capacity or inefficiency, ended up losing its connection with the HZ, throwing 30 years of work in the trash. The main man of the Quds Force was General Hossein Hamadani, the only man capable of replacing Soleimani at a high level; he was killed in 2015 by these rebel groups.
There is an Iranian foreign policy with Raisi and post-Raisi, Masoud Pezeshkian has shown that he has no strategic impetus to defend Iranian interests, although there was no way to save Syria without determination. Many criticize Russia and China for their lack of support in the Syrian issue, but Syria has never been fundamental to Russian and Chinese interests. The main interested party in Syria has always been Iran, so much so that it was Soleimani who convinced Putin to intervene when he went to Moscow to seek help.
Why didn't the US invade North Vietnam? Because the Americans knew that the Chinese would intervene. The Chinese did it in Korea, and China pushed the Americans beyond the 38th parallel, because China was committed to keeping more problems away from its borders. China did it in Korea and there is no doubt that it would do it in Vietnam as well. China did the right thing. Today, China has no border problems with Korea or Vietnam.
The Russian Federation, on the other hand, has a long history of failures. Russia does not deliver what it sells, does not do what it says, and has no red lines when its allies really need its support. I repeat here that Russia did absolutely nothing to stop the more than 500 airstrikes that undermined Syria's ability to rebuild and logistical lines, because there was an air route from Iran to Syria. These airports were systematically bombed. There is no way morale can be high when it is being bombed. No nation can withstand such humiliation and destruction. The Syrian state had no support to maintain its air sovereignty, because Iran's support was not only inefficient, but Syria was not helped by its other ally, Russia, because it had given Israel free rein to bomb whatever it wanted. Furthermore, Russia's priority is the Russian people. They are facing a coalition of countries in Ukraine, which ends up concentrating Russian resources on this conflict, leaving other theaters with minimal use of resources. However, one thing is certain: if the USSR were still standing today, the fall of Syria would not have actually happened, but the one that is there is the Russian Federation.
The dismantling of multi-ethnic federative states is a recurring practice of the US. They dismantled Yugoslavia and Libya, which was a tribal community, and now Syria. The US invented the concept of good criminals and evil criminals - the evil criminals are all those who do not follow the DoS playbook. They manage to make society work against their own interests through propaganda and coercion. The greatest proof is Ukraine, with them forcing Ukrainians to mobilize the youngest while Zelensky wants to prevent this.
Let's be honest:
The Gaza war is over and there is no longer a strategic objective, Gaza is ruined, all the Arab states that behaved like circus clowns, shouting against Israel, did absolutely nothing to help the Palestinians, this is a great lesson for AoR, as they ended up shooting themselves in the foot.
However, one thing I agree with
@Immortals that today's Iranian military is reaping the rewards of what their predecessors did, the new crop of Iranian military personnel do not seem as determined as the older generation who seemed to have fire in their blood.
The great generals seem to be a thing of the past, figures like Ali Sayyad Shirazi,
Valiollah Fallahi, Abbas Babaei, Mansour Sattari,
Ahmad Kazemi, Hassan Sateri, Hassan Tehrani Moghaddam, Ali Akbar Shiroodi, Javad Fakoori, Abbas Doran, Mostafa Ardestani, Hossein Khalatbari, Ali Eghbali Dogaheh, Mohammad-Vali Gharani, Mohammad Jahanar, Mohammad Boroujerdi, Husayn Kharrazi, Ahmad Keshvari, Ahmad Motevaselian, Hamid Bakeri, Mehdi Bakeri, Mohammad Ebrahim Hemmat, Hasan Bagheri, Mostafa Chamran, Mahmoud Kaveh, Hossein Hamadani, Qassem Soleimani, Seyed Hassan Firouzabadi, Mohammad Ali Jafari, Ataollah Salehi, Ali Shamkhani, Yahya Rahim Safavi, Mohammad Salimi, Ali Shahbazi, Mostafa Izadi, Hossein Hassani Sa'di among many others.